A continuous casting protective slag premelt base and a preparation process thereof

Abstract

The present application relates to continuous casting protective slag premelt base, specifically to a continuous casting protective slag premelt base and a preparation process thereof, wherein the mass percentage of the composition of the continuous casting protective slag premelt base is: boron-magnesium ore: 10-30%; limestone: 15-25%; feldspar: 7-22%; manganese ore: 1-7%; lithium mica: 11-23%; ilmenite: 2-13%; graphite: 1-2%; citric acid: 11-13%; polycarboxylic acid water reducing agent: 3-10%. The citric acid added in the continuous casting protective slag premelt base can generate calcium citrate precipitate with calcium oxide, and the generated insoluble substance will cover the surface of unhydrated material particles, hinder the dissolution of the substance, delay the start time of the protective slag precipitation period, thereby increasing the setting time of the continuous casting protective slag premelt base; the polycarboxylic acid water reducing agent added can make the continuous casting protective slag premelt base release more free water under the electrostatic repulsion of the ionized carboxylic acid particles, thereby increasing the fluidity of the continuous casting protective slag premelt base.

Description

Technical Field

[0001] This invention relates to the field of pre-melted matrix materials for continuous casting protective slag, and more specifically, to a pre-melted matrix material for continuous casting protective slag and its preparation process. Background Technology

[0002] In the continuous casting process of high-alumina steel, the aluminum in the molten steel readily undergoes redox reactions with components in the pre-melted flux of the continuous casting mold slag. This leads to a decrease in silica content and an increase in alumina content in the pre-melted flux, causing a significant change in its composition. Consequently, the performance of the pre-melted flux deteriorates, affecting its lubrication of the cast billet and its heat transfer control functions. This results in frequent defects such as slag entrapment and cracking during continuous casting, and even steel leakage due to adhesion. Excessive solidification rate of the pre-melted flux shortens the solidification time of the molten steel, impacting the quality of continuous casting production. Conversely, low fluidity of the pre-melted flux reduces its absorption efficiency, affecting the quality of the cast billet. Therefore, we propose a pre-melted flux with high fluidity and a longer solidification time. Summary of the Invention

[0003] The purpose of this invention is to provide a pre-melted base material for continuous casting protective slag and its preparation process, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, on the one hand, the present invention provides a pre-melted base material for continuous casting protective slag, the mass percentage of its components being: Boron-magnesium ore: 10-30%; Limestone: 15-25%; Feldspar: 7-22%; Manganese ore: 1-7%; Lithium mica: 11-23%; Ilmenite: 2-13%; Graphite: 1-2%; Citric acid: 11-13%; Polycarboxylate superplasticizer: 3-10%.

[0005] Preferably, the ratio of boron-magnesium ore to limestone is 1:0.8-1.

[0006] Preferably, the ratio of boromagnesia ore to feldspar is 1:0.6-0.8.

[0007] In the continuous casting process of high-alumina steel, aluminum in the molten steel undergoes redox reactions when it comes into contact with the liquid protective slag in the crystallizer, such as: 4Al + 3SiO2 = 3Si + 2Al2O3; 2Al + 3MnO = 3Mn + Al2O3; 2Al + B2O3 = 2B + Al2O3. This results in a significant decrease in the SiO2 content and a significant increase in the Al2O3 content in the protective slag. Studies have shown that during the continuous casting of high-alumina steel, the SiO2 content in the protective slag decreases by more than 10% due to the slag-steel reaction, while the Al2O3 content increases from 5% to 25%.

[0008] SiO2 is an acidic oxide that can adjust the basicity, viscosity, and crystallinity of protective slags, acting as a silicate network framework in the melt structure. In silicates, since the coordination number of oxygen is generally 4 and that of nitrogen is 2, the basic structural unit in silicates is mostly [SiO]. 4- Tetrahedrons, through their interconnection, can form complex silicate molecular structures. When the O / Si ratio in the protective slag is 4, independent [SiO] molecules will form. 4- Tetrahedral particles do not increase the viscosity of the protective slag; however, when the ratio is less than 4, they form negative ion aggregates, increasing the viscosity of the molten slag. The addition of Li₂O increases the oxygen ion content, thus reducing the viscosity of the molten slag. Li + Due to its smaller charge and larger radius, Li has a weaker affinity for oxygen ions, allowing it to provide more oxygen ions and increasing the O / Si ratio. This makes it easier for simple silicon-oxygen tetrahedra to form, and the negative ion aggregates to depolymerize more easily, thus reducing the viscosity of the slag. Furthermore, Li... + MnO can bond with silicon-oxygen tetrahedra, hindering the formation of silicon-oxygen tetrahedral network chains or directly breaking them, thus reducing the viscosity of the slag. The added MnO can also provide oxygen ions to the slag, breaking down complex silicon-oxygen anionic clusters, lowering the slag's viscosity activation energy, and consequently reducing the viscosity of the protective slag. MnO forms low-melting-point compounds in the slag, further reducing the melting temperature and viscosity of the protective slag.

[0009] The addition of TiO2 can react chemically with oxides in the slag to form stable compounds or chemical bonds, thereby improving the slag's resistance to slag erosion and reducing the likelihood of breakage of the pre-melted base material of the continuous casting protective slag under external pressure and due to collisions and friction between particles. At the same time, it can reduce the reaction and erosion between the slag and the metal surface, and improve the surface quality of the metal during the continuous casting process.

[0010] B2O3 is a low-melting-point acidic oxide that can significantly reduce the melting point and viscosity of protective slag, improve its physicochemical properties, and accelerate the dissolution of CaO.

[0011] Adding citric acid to the pre-melted base material of continuous casting protective slag can delay the setting time of the protective slag slurry. During the dissolution period, the calcium ions rapidly dissolved from various substances will first combine with the citrate ions dissolved from citric acid to form a small amount of water-insoluble calcium citrate. The chemical reaction equation is: 3CaO + 2C6H8O7 = (C6H5O7)2Ca3 + 3H2O. As a result, the ion concentration in the slurry system decreases. According to the precipitation theory, the insoluble substances generated by dissolution will cover the surface of the unhydrated material particles, hindering the dissolution of substances and delaying the start time of the protective slag precipitation period, thereby increasing the setting time of the pre-melted base material of continuous casting protective slag. At the same time, the retarding effect of citric acid delays the formation of hydration products to a certain extent. The formation of hydration products is accompanied by an increase in the amount of solid phase and a decrease in the amount of liquid phase in the system. Therefore, citric acid reduces the water content required for the reaction to a certain extent, increasing the fluidity of the pre-melted base material of continuous casting protective slag. The carboxylic acid in the added polycarboxylate superplasticizer can form a complex with the calcium ions generated during the dissolution period, reducing the calcium ion concentration in the water, inhibiting the crystallization of Ca(OH)2, and prolonging the nucleation period during hydration. In the flocculated structure of the pre-melted base material of continuous casting protective slag, there are more porous solutions. Under the electrostatic repulsion of carboxyl ions ionized from the carboxyl groups in the polycarboxylate superplasticizer, more free water is released from the flocculated structure, increasing the fluidity of the pre-melted base material slurry. When the pre-melted base material melts at high temperatures, some components undergo chemical reactions, producing free carbon dioxide gas. Simultaneously, the viscosity of the pre-melted base material decreases. Excessively low viscosity allows slag components involved in the reaction to enter the molten steel, increasing oxide inclusions in the steel and easily leading to "secondary cracks" on the surface of the continuously cast billet. The presence of free water can increase the viscosity of the pre-melted base material, reducing this phenomenon.

[0012] Preferably, the preparation method of the pre-melted base material for continuous casting protective slag is as follows: S1: Weigh the raw materials prepared according to the percentage of the pre-melted base material of the continuous casting protective slag; S2: Grind and crush various raw materials, and then mix them using mechanical mixing equipment to ensure that the various substances are mixed evenly; S3: Adjust the temperature and mixing time parameters of the mixing system to promote the interaction and stability between particles; S4: React and solidify the mixture at an appropriate temperature to allow chemical reactions or the formation of a stable structure among the various components in the pre-melted base material of continuous casting protective slag. S5: Cool and grind the solidified mixture to obtain the pre-melted base material of continuous casting protective slag.

[0013] Preferably, the particle size of the raw material grinding particles in S2 is 30-40 μm; Preferably, the mechanical stirring equipment has a rotation speed of 1200-1400 r / min and a stirring time of 2-3 h.

[0014] Preferably, the reaction temperature in S4 is 1400-1600℃ and the reaction time is 2-3h.

[0015] Preferably, the curing temperature in S5 is 400-800℃ and the curing time is 1-2 days.

[0016] Preferably, the grinding particle size in S5 is 400-500 mesh.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The added citric acid can react with calcium oxide to form calcium citrate precipitate. The resulting insoluble substance will cover the surface of unhydrated material particles, hindering the dissolution of the substance and delaying the start time of the protective slag settling period, thereby increasing the setting time of the continuous casting protective slag pre-melted base material. The added polycarboxylate superplasticizer can enable the continuous casting protective slag pre-melted base material to release more free water under the electrostatic repulsion of the ionized carboxylate particles, thereby increasing the fluidity of the continuous casting protective slag pre-melted base material. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0019] The following embodiments of the present invention are used: The boron-magnesium ore, limestone, feldspar, manganese ore, lepidolite, and ilmenite were all purchased from Xinyu Siyuan Mining Co., Ltd.

[0020] The graphite was purchased from Baotou Steel Co., Ltd., CAS No. 7782-42-5.

[0021] Citric acid was purchased from Cangzhou Xinjia Chemical Products Co., Ltd., CAS No. 77-92-9.

[0022] The polycarboxylate superplasticizer was purchased from Henan Tongxu Chemical Products Co., Ltd. Example 1

[0023] Preparation of pre-melted base material for continuous casting protective slag: S1: Weigh the raw materials according to the mass percentage of the components of the pre-melted base material for continuous casting protective slag and mix them, wherein, Boron-magnesium ore: 20%; Limestone: 16%; Feldspar: 14%; Manganese ore: 4%; Lithium mica: 17%; Ilmenite: 7.5%; Graphite: 1.5%; Citric acid: 12%; Polycarboxylate superplasticizer: 6.5%.

[0024] S2: Grind and crush various raw materials to a particle size of 35μm, and then mix them using a mechanical stirring device. The mechanical stirring device rotates at 1300r / min and the stirring time is 2.4h to ensure that the various substances are mixed evenly. S3: Adjust the temperature and mixing time parameters of the mixing system to promote the interaction and stability between particles; S4: The mixture is reacted and solidified at 1500℃ for 3 hours, so that the various components in the pre-melted base material of continuous casting protective slag undergo chemical reactions or form a stable structure. S5: The mixture cured at 500℃ for 1 day is cooled and ground to a particle size of 500 mesh to obtain test sample 1.

[0025] Example 2 Preparation of pre-melted base material for continuous casting protective slag: S1: Weigh the raw materials according to the mass percentage of the components of the pre-melted base material for continuous casting protective slag and mix them, wherein, Boron-magnesium ore: 18%; Limestone: 16%; Feldspar: 14%; Manganese ore: 4%; Lithium mica: 17%; Ilmenite: 7.5%; Graphite: 1.5%; Citric acid: 12%; Polycarboxylate superplasticizer: 6.5%.

[0026] S2: Grind and crush various raw materials to a particle size of 35μm, and then mix them using a mechanical stirring device. The mechanical stirring device rotates at 1300r / min and the stirring time is 2.4h to ensure that the various substances are mixed evenly. S3: Adjust the temperature and mixing time parameters of the mixing system to promote the interaction and stability between particles; S4: The mixture is reacted and solidified at 1500℃ for 3 hours, so that the various components in the pre-melted base material of continuous casting protective slag undergo chemical reactions or form a stable structure. S5: The mixture cured at 500℃ for 1 day will be cooled and ground to a particle size of 500 mesh to obtain test sample 2.

[0027] Example 3 Preparation of pre-melted base material for continuous casting protective slag: S1: Weigh the raw materials according to the mass percentage of the components of the pre-melted base material for continuous casting protective slag and mix them, wherein, Boron-magnesium ore: 18%; Limestone: 15%; Feldspar: 14%; Manganese ore: 4%; Lithium mica: 17%; Ilmenite: 7.5%; Graphite: 1.5%; Citric acid: 12%; Polycarboxylate superplasticizer: 6.5%.

[0028] S2: Grind and crush various raw materials to a particle size of 35μm, and then mix them using a mechanical stirring device. The mechanical stirring device rotates at 1300r / min and the stirring time is 2.4h to ensure that the various substances are mixed evenly. S3: Adjust the temperature and mixing time parameters of the mixing system to promote the interaction and stability between particles; S4: The mixture is reacted and solidified at 1500℃ for 3 hours, so that the various components in the pre-melted base material of continuous casting protective slag undergo chemical reactions or form a stable structure. S5: The mixture cured at 500℃ for 1 day will be cooled and ground to a particle size of 500 mesh to obtain test sample 3.

[0029] Example 4 Preparation of pre-melted base material for continuous casting protective slag: S1: Weigh the raw materials according to the mass percentage of the components of the pre-melted base material for continuous casting protective slag and mix them, wherein, Boron-magnesium ore: 20%; Limestone: 16%; Feldspar: 14%; Manganese ore: 4%; Lithium mica: 17%; Ilmenite: 7.5%; Graphite: 1.5%; Citric acid: 11%; Polycarboxylate superplasticizer: 6.5%.

[0030] S2: Grind and crush various raw materials to a particle size of 35μm, and then mix them using a mechanical stirring device. The mechanical stirring device rotates at 1300r / min and the stirring time is 2.4h to ensure that the various substances are mixed evenly. S3: Adjust the temperature and mixing time parameters of the mixing system to promote the interaction and stability between particles; S4: The mixture is reacted and solidified at 1500℃ for 3 hours, so that the various components in the pre-melted base material of continuous casting protective slag undergo chemical reactions or form a stable structure. S5: The mixture cured at 500℃ for 1 day will be cooled and ground to a particle size of 500 mesh to obtain test sample 4.

[0031] Example 5 Preparation of pre-melted base material for continuous casting protective slag: S1: Weigh the raw materials according to the mass percentage of the components of the pre-melted base material for continuous casting protective slag and mix them, wherein, Boron-magnesium ore: 20%; Limestone: 16%; Feldspar: 14%; Manganese ore: 4%; Lithium mica: 17%; Ilmenite: 7.5%; Graphite: 1.5%; Citric acid: 12%; Polycarboxylate superplasticizer: 7.5%.

[0032] S2: Grind and crush various raw materials to a particle size of 35μm, and then mix them using a mechanical stirring device. The mechanical stirring device rotates at 1300r / min and the stirring time is 2.4h to ensure that the various substances are mixed evenly. S3: Adjust the temperature and mixing time parameters of the mixing system to promote the interaction and stability between particles; S4: The mixture is reacted and solidified at 1500℃ for 3 hours, so that the various components in the pre-melted base material of continuous casting protective slag undergo chemical reactions or form a stable structure. S5: The mixture cured at 500℃ for 1 day will be cooled and ground to a particle size of 500 mesh to obtain test sample 5.

[0033] Comparative Example 1 Using the same formulation and preparation process as in Example 1, the only difference being that citric acid was not added, test sample 6 was obtained.

[0034] Comparative Example 2 Using the same formulation and preparation process as in Example 1, the only difference being that no polycarboxylate superplasticizer was added, test sample 7 was obtained.

[0035] The viscosity and flowability of the obtained test samples were measured, and the results are shown in the table below:

[0036] Comparing samples 1, 2, and 3 reveals that excessively high or low calcium carbonate ratios negatively impact the viscosity of the pre-melted matrix of the continuous casting molded slag. Comparing samples 1, 4, and 6 shows that the addition of citric acid increases the fluidity of the pre-melted matrix; however, changes in calcium oxide content also affect fluidity. Comparing samples 1, 4, and 7 reveals that the addition of polycarboxylate superplasticizers also affects the fluidity of the pre-melted matrix, exhibiting a similar effect to citric acid. Therefore, adding citric acid and polycarboxylate superplasticizers to the pre-melted matrix of the continuous casting molded slag can increase its fluidity and also have a certain effect on viscosity.

[0037] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pre-melted base material for continuous casting protective slag, characterized in that: Its constituent components by mass percentage are: Boron-magnesium ore: 10-30%; Limestone: 15-25%; Feldspar: 7-22%; Manganese ore: 1-7%; Lithium mica: 11-23%; Ilmenite: 2-13%; Graphite: 1-2%; Citric acid: 11-13%; Polycarboxylate superplasticizer: 3-10%; The ratio of boron-magnesium ore to limestone is 1:0.8-1; The boron-magnesium ore:feldspar ratio is 1:0.6-0.

8.

2. A preparation process for the pre-melted base material of continuous casting protective slag as described in claim 1, characterized in that... The preparation method of the pre-melted base material for continuous casting protective slag is as follows: S1: The raw materials prepared by weighing the percentage of the pre-melted base material of the continuous casting protective slag; S2: Grind and crush various raw materials, and then mix them using mechanical mixing equipment to ensure that the various substances are mixed evenly; S3: Adjust the temperature and mixing time parameters of the mixing system to promote the interaction and stability between particles; S4: React and solidify the mixture at an appropriate temperature to allow chemical reactions or the formation of a stable structure among the various components in the pre-melted base material of continuous casting protective slag. S5: Cool and grind the solidified mixture to obtain the pre-melted base material of continuous casting protective slag.

3. The preparation process of the pre-melted base material for continuous casting protective slag according to claim 2, characterized in that... The particle size of the raw material grinding particles in S2 is 30-40μm.

4. The preparation process of the pre-melted base material for continuous casting protective slag according to claim 2, characterized in that... The mechanical mixing equipment operates at a speed of 1200-1400 r / min and a mixing time of 2-3 hours.

5. The preparation process of the pre-melted base material for continuous casting protective slag according to claim 2, characterized in that... The reaction temperature in S4 is 1400-1600℃; the reaction time is 2-3h.

6. The preparation process of the pre-melted base material for continuous casting protective slag according to claim 2, characterized in that... The curing temperature in S5 is 400-800℃; the curing time is 1-2 days.

7. The preparation process of the pre-melted base material for continuous casting protective slag according to claim 2, characterized in that... The grinding particle size in S5 is 400-500 mesh.

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