Continuous casting covering slag with high self-adaptability and preparation method

Abstract

The invention provides continuous casting covering slag with high self-adaptability and a preparation method, and belongs to the field of continuous casting process auxiliary materials. The casting powder comprises, by mass, 14.1%-17.2% of CaO, 12.5%-33.6% of SiO2, 14.3%-25.1% of Al2O3, 19.6%-23.8% of NaF, 1.8%-2.3% of MgO, 0%-4.8% of Li2O, 2.3%-4.1% of MnO, 3.6%-9.6% of CaF2, 2.8%-5.5% of C and inevitable impurities, the atomic ratio of O to F is 2 to 3, and the atomic ratio of Si to Al is 0.3 to 2. By controlling the ratio of fluorine to oxygen, destroying the network high polymerizability of a silicon-oxygen structure and an aluminum-oxygen structure, changing the melting point and viscosity of slag and controlling the ratio of Si to Al, it is guaranteed that the melting point and viscosity are within a reasonable range, the situation that the melting point is greatly increased and the viscosity is suddenly increased due to the fact that SiO2 or Al2O3 is too high is avoided, and the protection effect is improved.

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] In order to solve the above problems, the present invention provides a continuous casting mold slag with high adaptability and a preparation method thereof, by controlling the atomic ratio of F and O, and the atomic ratio of Al and Si, so that fluorine atoms replace oxygen anions, form Si-F bonds in silicon-oxygen tetrahedrons, reduce the bridging oxygen of the network structure formed by silicon and oxygen anion units, and form more mono-bridge oxygen (Q 1 ) and di-bridged oxygen (Q 2 ) and other simple structures, while reducing the high-bridge oxygen forms of oxygen atoms in the silicon-oxygen tetrahedron, such as the triple-bridge oxygen (Q 3 ) or four-bridge oxygen (Q 4 ), reducing the degree of polymerization of silicon-oxygen tetrahedrons; at the same time, among the Al-F bond and the Al-O bond, the Al-F bond energy is smaller than the Al-O bond, and fluoride ions are used to replace the oxygen atoms in the Al-O anion group to form an aluminum oxygen complex ion 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 protective slag; at the same time, for high-manganese and high-aluminum molten steel, after the protective slag reacts with the molten steel, such as the reaction of SiO2 and [Al], the physical and chemical properties of the protective slag do not change drastically, and the new protective slag melting supplement and the protective slag entering the slag channel consumption reach a balance, adapting to the strong reaction characteristics of high-manganese and high-aluminum steel, thereby achieving high adaptability.

[0007] In order to achieve the above object, the technical solution adopted by the embodiment of the present invention is as follows:

[0008] In a first aspect, an embodiment of the present invention provides a continuous casting mold slag with high adaptability, wherein the mold slag comprises, by mass percentage: CaO 14.1%~17.2%, SiO2 12.5%~33.6%, Al2O3 14.3%~25.1%, NaF19.6%~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, wherein the atomic ratio of O to F in the continuous casting mold slag is 2.1~3.0, and the atomic ratio of Si to Al is 0.4~2.0.

[0009] In the protective slag, by adding NaF and CaF2 at the same time and controlling the ratio of fluorine to oxygen, on the one hand, sufficient F ions are provided so that the F ions can replace the oxygen ions in Si-O and Al-O of the silicon-oxygen tetrahedron under a high-temperature molten working state, thereby destroying the high polymerization of the network of silicon-oxygen structure and aluminum-oxygen structure; on the other hand, the atomic ratio of O and F is controlled to be 2-3. Under the premise of providing sufficient oxygen substitution, the protective slag with an oxygen-fluorine ratio of less than 2.0 has too high a fluoride content, which is easy to volatilize during use, resulting in a change in the properties of the protective slag and causing environmental pollution.

[0010] Fluoride ions have a destructive effect on silicon-oxygen structures and aluminum-oxygen structures. The core is that fluoride ions have strong electronegativity and high activity, which are specifically manifested in three aspects: replacement of chemical bonds, loosening of network structure, and disturbance of charge balance. In the network structure of protective slag, 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 silicon-oxygen tetrahedrons or aluminum-oxygen tetrahedrons to form Si-F bonds or Al-F bonds. This substitution reduces the stability of the tetrahedral structure. After fluoride ions replace bridging oxygen, the Si-F bonds and Al-F bonds formed are terminal bonds and are no longer connected to other structural units, resulting in high polymerization degree Q in the network. 4 The ratio is reduced, and the Q of low polymerization degree 1 and Q 2 As the ratio increases, the long-chain or cyclic silicon-oxygen structure decreases, resulting in a decrease in the three-dimensional connectivity of the tetrahedral structure and a looser network structure. The high nucleophilicity of fluoride ions allows them to preferentially form bonds with cations, weakening the ability of cations to bind to 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 tetrahedron to octahedron. The formation of this high-coordinated aluminum further destroys the stability of the network structure. In low oxygen-fluorine ratio (2.0~3.0) protective slag, aluminum ions mainly exist in a four-coordinate form, and fluoride ions will replace one or two oxygen ions in the aluminum-oxygen tetrahedron to form a network structure dominated by AlO3F and AlO2F2. In traditional protective slags with an oxygen-fluorine ratio greater than 5.0, there must be a large number of AlO4 structures and a small amount of Al-OF structures. The introduction of fluoride ions will form terminal bonds Al-F, destroy the bridging oxygen bonds, reduce the network rigidity and connectivity of aluminum-oxygen molecular groups, 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 oxide nucleus, release more free oxygen ions, further reduce the bridging oxygen in AlO3F and AlO2F2, and form excessive AlO2F2 or AlOF3 structures, which improves the Q of the aluminum oxide network. 3 The proportion of bridging oxygen structure decreases, Q 2 and Q 1The increase in the proportion of bridging oxygen structure further reduces the melting point and viscosity of the mold slag.

[0011] At the same time, limiting the atomic ratio of Si and Al to 0.3~2 and controlling the silicon-aluminum ratio in the protective slag can ensure that the melting point and viscosity of the protective slag are within a reasonable range, avoiding the problem of a sharp increase in the melting point of the protective slag and a sudden increase in viscosity due to excessive SiO2 or Al2O3 in the slag.

[0012] The addition of MnO can effectively adjust the color of the protective slag film, which is beneficial to control heat transfer and prevent the occurrence of defects such as slab depression and cracks.

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

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

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

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

[0017] In a preferred embodiment, the fluctuation range of the consumption of the continuous casting protection slag after working in the crystallizer for 20 minutes is within 20%.

[0018] In a second aspect, an embodiment of the present invention further provides a method for preparing a highly adaptive continuous casting mold slag, the method comprising:

[0019] 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%, SiO212.5%~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%, and the rest are inevitable impurities; wherein, in the continuous casting mold slag, the atomic ratio of O to F is 2.1~3.0, and the atomic ratio of Si to Al is 0.4~2.0;

[0020] Step S2, heating the mixed raw material to a molten state, and keeping the mixture in the molten state for a predetermined time to remove volatile components to obtain a slag with uniform composition; the predetermined holding time here is generally 10 minutes to 2 hours;

[0021] Step S3, quenching the molten slag with water to obtain a glassy slag sample;

[0022] Step S4, crushing and sieving the slag sample to obtain a powder sample of a predetermined particle size; the predetermined particle size here is 300-700 mesh;

[0023] Step S5, adding 2.8% to 5.5% of carbonaceous material by mass percentage to the powder sample, and then adding a binder, a dispersant and water, stirring evenly to obtain a mixed slurry; the amount of the binder is 0.1-0.8wt%, and the amount of the dispersant is 0.5-2.0wt%; preferably, the binder is cellulose, and the dispersant is sodium methylnaphthalene sulfonate;

[0024] Step S6, drying and sieving the mixed slurry, and then granulating to obtain protective slag. In this step, the drying requires a moisture content of <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 highly adaptive continuous casting protection slag and preparation method provided in the embodiment of the present invention, by limiting the fluorine-oxygen ratio, under the condition of ensuring sufficient substitution of fluorine for oxygen, destroy the high polymerization of the network of silicon-oxygen structure and aluminum-oxygen structure, reduce the stability of the silicon-oxygen tetrahedral network structure, form a low-dimensional structure based on Al-O, reduce the number of network structures, and thus reduce the melting point and viscosity of the protection slag; at the same time, the atomic ratio of Si and Al is controlled to be 0.3-2, and the silicon-aluminum ratio in the protection slag is controlled to ensure that the melting point and viscosity of the protection slag are within a reasonable range, avoiding excessive conductivity of SiO2 or Al2O3 in the slag The problem of a sharp increase in the melting point of the protective slag and a sudden increase in the viscosity caused by the protective slag is solved. The physical and chemical properties of the protective slag do not change drastically. The melting and replenishment of new protective slag and the consumption of protective slag entering the slag channel reach a balance, which adapts to the strong reaction characteristics of high manganese and high aluminum steel, thereby achieving high adaptability; the continuous casting protective slag can form a stable liquid layer with good lubrication effect, which can well ensure the smooth continuous casting of multiple furnaces, effectively prevent the occurrence of defects such as dents and cracks in the casting, and enable the protective slag to better play the role of heat insulation, oxidation prevention, inclusion absorption, billet shell lubrication and heat transfer control, thereby improving the protection effect on molten steel.

[0027] Of course, it is not necessary to achieve all of the advantages described above at the same time to implement any product or method of the present invention. DETAILED DESCRIPTION

[0028] After discovering the above problems, the inventors of this application have conducted a detailed study on the existing continuous casting protection slag, especially the protection slag materials used in high manganese and high aluminum molten steel. The study found that according to the coexistence theory, in the high-temperature melt of the protection slag, components such as CaO, Na2O, and MgO will decompose to form simple cations and free oxygen ions; anionic groups mainly composed of silicon-oxygen tetrahedrons will be formed in the CaO-SiO2-based protection slag, in which O atoms will exist in the form of bridging oxygens, connecting multiple silicon-oxygen tetrahedrons to form macromolecular groups with complex network structures; 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 or monomer structures, resulting in a decrease in the melting point and viscosity of the protection slag. In comparison, the free oxygen ions have limited effect on destroying the Al-O structure in the CaO-Al2O3-based protection slag, and macromolecular groups with complex network structures will be formed in the melt, which increases the melting point and viscosity of the protection slag. If a high-basicity CaO-Al2O3-based weak (non-) reactive mold slag is used in the continuous casting process, reducing or avoiding the use of SiO2 in the mold slag is beneficial to reducing the slag-steel reaction and controlling the change in the mold slag composition and the deterioration of its performance. However, it is difficult for free oxygen ions to destroy the large-sized molecular groups in the CaO-Al2O3-based mold slag, resulting in poor melting, easy slag rings and low consumption. It is rarely used in actual production.

[0029] Therefore, whether it is CaO-SiO2-based or CaO-Al2O3-based high manganese and high aluminum steel protection slag, the key to solving the melting point and viscosity lies in controlling the large-sized network anion groups. Silicon and oxygen are connected by covalent bonds to form anion units, which serve as network formers to form a network structure of silicon-oxygen tetrahedrons, in which most oxygen atoms exist in the form of high-bridge oxygen, such as triple-bridge oxygen (Q 3 ) or four-bridge oxygen (Q 4 ), and fluorine atoms can replace the bridging oxygen of this highly polymerized network structure to form more single-bridge oxygen (Q 1 ) and di-bridged oxygen (Q 2 ) and other simple structures to reduce the degree of polymerization of silicon-oxygen tetrahedrons; the bond lengths of Al-F and Al-O are 0.1895 nm and 0.1745 nm respectively, and the bond energy of Al-F is smaller than that of Al-O, so fluoride ions are used to replace oxygen atoms in anionic groups to form aluminum oxygen complex ions Al2OF6 2- and Al2O2F4 2- , which will destroy the stability of the bridging oxygen structure in Al2O3 and reduce the number of network structures, thereby lowering the melting point and viscosity of the protective slag.

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

[0031] Based on the above in-depth analysis, the embodiment of the present invention proposes a continuous casting protective slag with high adaptability and a preparation method. The following will be clearly and completely described in combination with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] 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.

[0034] The continuous casting protection slag includes, by mass percentage, the following: CaO 15.4%, SiO2 30.2%, Al2O3 15.8%, NaF2 3.1%, MgO 2.3%, Li2O 3.5%, MnO 2.3%, CaF2 3.6%, C 3.5%, and the rest are unavoidable impurities. At this time, the atomic ratio of O and F in the continuous casting protection slag is 3, and the atomic ratio of Si and Al is 1.6.

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

[0036] 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;

[0037] 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;

[0038] Step S3, quenching the molten slag with water to obtain a glassy slag sample;

[0039] 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%;

[0040] 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;

[0041] Step S6, using a spray granulation drying tower to dry and granulate the mixed slurry, the evenly mixed mud 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. The small droplets form round spheres under the action of 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°C, and the outlet wind temperature is 160°C. The drying requires a moisture content of less than 0.5%; the dried hollow particle protective slag is sieved in a closed vibrating screen, and the granulation particle size is 0.01-1.8mm. The protective slag particles are transported to the finished product silo by a belt conveyor.

[0042] The melting temperature of the continuous casting mold slag obtained in this embodiment is 848°C, the viscosity is 2 Pa·s at 1300°C, the crystal phase is chalcite, the volatilization amount at 1500°C is 1.89%, and the initial slag consumption is 0.34 kg / m 2 , the slag consumption after 20 minutes is 0.3kg / m 2 .

[0043] Example 2

[0044] This embodiment also provides a continuous casting protection slag with high adaptability and a preparation method thereof. The continuous casting protection slag is particularly suitable for the casting of high manganese and high aluminum steel.

[0045] The continuous casting protection slag includes, by mass percentage, the following: CaO 17.2%, SiO2 33.6%, Al2O3 14.3%, NaF19.6%, MgO 1.9%, MnO 2.3%, CaF2 7.4%, C 3.8%, and the rest are unavoidable impurities. At this time, the atomic ratio of O and F in the continuous casting protection slag is 2.7, and the atomic ratio of Si and Al is 2.

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

[0047] 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 through a 50 μm (300 mesh) sieve; all the raw materials are added into a stirrer and stirred for 30 minutes to obtain a uniform mixed raw material;

[0048] Step S2, heating the mixed raw materials to 1500°C to melt, and keeping the temperature for 30 minutes to obtain slag with uniform composition, which is qualified after chemical testing;

[0049] Step S3, quenching the molten slag with water to obtain a glassy slag sample;

[0050] 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 50 μm (300 mesh) sieve, and the sieve residue is not greater than 5%;

[0051] 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;

[0052] Step S6, using a spray granulation drying tower to dry and granulate the mixed slurry, the evenly mixed mud 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. The small droplets form round spheres under the action of 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°C, and the outlet wind temperature is 160°C. The drying requires a moisture content of less than 0.5%; the dried hollow particle protective slag is sieved in a closed vibrating screen, and the granulation particle size is 0.01-1.8mm. The protective slag particles are transported to the finished product silo by a belt conveyor.

[0053] The melting temperature of the continuous casting mold slag obtained in this embodiment is 1001°C, the viscosity is 1.34 Pa·s at 1300°C, the crystal phase is chalcite and sodium calcium aluminate, the volatilization amount at 1500°C is 1.69%, and the initial slag consumption is 0.41 kg / m 2 , the slag consumption after 20 minutes is 0.34kg / m 2 .

[0054] Example 3

[0055] 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.

[0056] The continuous casting protection slag includes, by mass percentage, the following: CaO 14.1%, SiO2 18.2%, Al2O3 24.5%, NaF2 0.2%, MgO 2.0%, Li2O 4.5%, MnO 4.1%, CaF2 9.6%, C 2.8%, and the rest are unavoidable impurities. At this time, the atomic ratio of O and F in the continuous casting protection slag is 2.5, and the atomic ratio of Si and Al is 0.6.

[0057] The preparation method of the continuous casting mold slag 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 protection slag includes, by mass percentage, the following: CaO 14.2%, SiO2 12.5%, Al2O3 25.1%, NaF2 3.8%, MgO 1.8%, Li2O 4.8%, MnO 3.6%, CaF2 8.7%, C 5.5%, and the rest are unavoidable impurities. At this time, the atomic ratio of O and F in the continuous casting protection slag is 2.1, and the atomic ratio of Si and Al is 0.4.

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

[0069] 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;

[0070] 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;

[0071] Step S3, quenching the molten slag with water to obtain a glassy slag sample;

[0072] 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%;

[0073] 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;

[0074] 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.

[0075] The melting temperature of the continuous casting mold slag obtained in this embodiment is 1077°C, the viscosity is 1.06 Pa·s at 1300°C, the crystal phase is calcium sodium aluminate, the volatility at 1500°C is 1.95%, and the initial slag consumption is 0.51 kg / m 2, slag consumption after 20 minutes is 0.42kg / m 2 .

[0076] Comparative Example 1

[0077] A continuous casting mold slag comprises, by mass percentage, 30.8% CaO, 7.1% SiO2, 29.2% Al2O3, 5.2% NaF1, 1.1% MgO, 3.5% Li2O, 2.4% MnO, 5.2% CaF2, 5.5% C, and the rest are unavoidable impurities. At this time, the atomic ratio of O to F in the continuous casting mold slag is 6.4, and the atomic ratio of Si to Al is 0.21.

[0078] The preparation method of the continuous casting protection slag is the same as the preparation method of Example 1, except for the ratio of raw materials. This comparative example adopts the ratio of raw materials in the comparative example.

[0079] The results show that the melting temperature of the continuous casting mold slag obtained in this comparative example is 1168°C, the viscosity at 1300°C is 0.961 Pa·s, the crystal 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 , slag consumption after 20 minutes is 0.11kg / m 2 .

[0080] Comparative Example 2

[0081] A continuous casting mold slag comprises, by mass percentage, 14% CaO, 10% SiO2, 35% Al2O3, 24% NaF, 3.5% MgO, 6% Li2O, 3.5% MnO, 9% CaF2, 5.5% C, and the remainder being unavoidable impurities. At this time, the atomic ratio of O to F in the continuous casting mold slag is 6.4, and the atomic ratio of Si to Al is 0.21.

[0082] The preparation method of the continuous casting protection slag is the same as the preparation method of Example 1, except for the ratio of raw materials. This comparative example adopts the ratio of raw materials in the comparative example.

[0083] The melting temperature of the continuous casting mold slag obtained in this embodiment is 1220°C, the viscosity is 1.247 Pa·s at 1300°C, the crystal phase is pyroxene and lanceolite, the volatilization amount at 1500°C is 1.51%, and the initial slag consumption is 0.38 kg / m 2 , slag consumption after 20 minutes is 0.13kg / m 2 .

[0084] Comparative Example 3

[0085] A continuous casting mold slag comprises, by mass percentage, 13.5% CaO, 35% SiO2, 11.6% Al2O3, 9.5% NaF1, 1.9% MgO, 2.5% MnO, 9.5% CaF2, 6% C, and the remainder being unavoidable impurities. At this time, the atomic ratio of O to F in the continuous casting mold slag is 2.5, and the atomic ratio of Si to Al is 3.

[0086] The preparation method of the continuous casting protection slag is the same as the preparation method of Example 1, except for the ratio of raw materials. This comparative example adopts the ratio of raw materials in the comparative example.

[0087] The melting temperature of the continuous casting mold slag obtained in this embodiment is 1044°C, the viscosity is 0.18 Pa·s at 1300°C, the crystal phase is gunite and calcium fluoride, the volatilization amount at 1500°C is 5.68%, and the initial slag consumption is 0.86 kg / m 2 , the slag consumption after 20 minutes is 0.55kg / m 2 .

[0088] Comparative Example 4

[0089] A continuous casting mold slag comprises, by mass percentage, 15.8% CaO, 10% SiO2, 30% Al2O3, 2.5% NaF2, 3% MgO, 4.5% Li2O, 3% MnO, 9% CaF2, 3.9% C, and the remainder being unavoidable impurities. At this time, the atomic ratio of O to F in the continuous casting mold slag is 3, and the atomic ratio of Si to Al is 0.2.

[0090] The preparation method of the continuous casting protection slag is the same as the preparation method of Example 1, except for the ratio of raw materials. This comparative example adopts the ratio of raw materials in the comparative example.

[0091] The melting temperature of the continuous casting mold slag obtained in this embodiment is 1254°C, the viscosity is 5.15 Pa·s at 1300°C, the crystal phase is chalcite and sodium calcium aluminate, the volatilization amount at 1500°C is 2.68%, and the initial slag consumption is 0.18 kg / m 2 , the slag consumption after 20 minutes is 0.09kg / m 2 .

[0092] By comparing Examples 1 to 4 of the present invention with Comparative Examples 1 to 4, it can be seen that in Examples 1 to 4, the oxygen-fluorine ratio of the protective slag 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 composed of pyroxene and calcium silicon aluminate. Comparative Examples 1 and 2 are traditional CaO-SiO2-based and CaO-Al2O3-based protective slags, and the oxygen-fluorine ratio is relatively high. SiO2 in the CaO-SiO2-based protective slag is very easy to react with [Al] in the steel, resulting in a drastic change in the composition of the protective slag and an increase in the Al2O3 content; the Al2O3 content of the CaO-Al2O3-based low (non) reactive protective slag steel will also increase after the reaction. The Al2O3 content in the two protective slags will generally reach more than 40%. Excessive Al2O3 will cause the performance of the protective slag to deteriorate after a period of time, the slag consumption will be reduced, the protective slag will not be updated in time, the residence time will increase, the protective slag composition and performance will continue to deteriorate, and continuous casting will be difficult.

[0093] In Examples 1 to 4, the initial slag consumption is equivalent to that in Comparative Examples 1 to 2. After 20 minutes of casting, the slag consumption decreases slightly, but the slag consumption is generally maintained at a normal level. In the case of large slag consumption, the protective slag is added to the liquid slag layer in time after melting, and the protective slag is maintained to be rapidly updated, which offsets the composition changes caused by the reduction of part of SiO2, and has good lubrication, avoiding slag removal and slag replacement operations, ensuring the smooth development of continuous casting, and improving the surface depressions, cracks and other defects of the produced ingots, and increasing the continuous casting of high manganese and high aluminum steel. In Comparative Example 3, the melting point of the protective slag is low, the thick liquid slag layer leads to a large consumption of protective slag, and the thickness of the formed slag film increases, which is not conducive to controlling the heat transfer between the ingot shell and the copper plate. At the same time, the excessively high NaF content leads to a large volatilization 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, the slag consumption is too low, and the lubrication effect can basically not be played.

[0094] In Examples 1-4, the initial slag consumption and 20-min slag consumption are moderate, the crystal phase is stable, the volatilization amount during continuous casting is less than 2%, and the Al2O3 inclusions in the steel float to the slag interface and are absorbed by the protective slag. The protective slag has excellent inclusion absorption performance.

[0095] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. It is not intended to limit the scope of the invention claimed for protection, but only represents the preferred embodiment 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 solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned 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 making creative work belong to 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. Wherein, the atomic ratio of O to F in the continuous casting mold slag is 2.1-3.0, and the atomic ratio of Si to Al is 0.4-2.

0.

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 viscosity of the continuous casting mold slag at 1300° C. is 1.06-2.00 Pa·s.

4. 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.

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

6. 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%.

7. A method for preparing continuous casting mold slag according to any one of claims 1 to 6, 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 2.1~3.0, 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 and sieving the mixed slurry, and then granulating it to obtain protective slag.

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

9. The preparation method according to claim 7, 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.

10. The preparation method according to claim 7, characterized in that: In step S6, the drying requires a moisture content of less than 0.5 wt.%, and a granulation size of 0.01-1.8 mm.