Continuous casting protective agent based on sno2-fe2o3 molten salt system and preparation process thereof

Abstract

The application relates to the field of continuous casting protective slag, in particular to a continuous casting protective slag based on a SnO2-Fe2O3 molten salt system and a preparation process thereof. The mass percentage of the constituent components is as follows: SnO2: 18-38%; Fe2O3: 12-30%; Al2O3: 6-16%; SiO2: 4-16%; Gd2O3: 3-7%; CeO2: 4-9%; B2O3: 3-8%; TiO2: 8-20%; C: 1-3%; and the rest is inevitable impurities. The SnO2-Fe2O3 molten salt system is used as a basic material, has a low melting point, viscosity and good thermal stability, TiO2 and B2O3 are added to replace fluorides, the melting point and viscosity of the protective slag can be reduced, the rare earth oxides Gd2O3 and CeO2 are added to enhance the crystallization ability of the protective slag, reduce defects such as air holes and cracks on the surface of the cast slab, and improve the compactness and mechanical properties of the cast slab.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of continuous casting protective slag, in particular to a continuous casting protective slag based on SnO2-Fe2O3 molten salt system and a preparation process thereof. BACKGROUND

[0002] Continuous casting protective slag is a slag material covering the surface of molten steel in a continuous casting crystallizer and capable of maintaining the normal casting process of continuous casting. With the expansion of continuous casting protective slag varieties and the improvement of quality requirements for protective slag, the protective slag is developing in the direction of specialization to ensure the stability of raw material composition. When the melting point of the protective slag is too high, it cannot well wet the surface to be protected, reduces its protection effect, causes cracks on the surface to be protected, and the high melting point of the protective slag requires higher temperature to melt, requires higher energy cost and time, and affects the efficiency of the process. When the viscosity of the continuous casting protective slag is too high, it will affect the quality of the casting blank, reduce the lubricating effect of the protective slag, affect the formation of the slag liquid on the surface of the molten steel, cause sintered particles in the molten layer, and also increase the consumption of the protective slag, resulting in uneven thickness of the slag film. In view of this, the present application provides a continuous casting protective slag based on SnO2-Fe2O3 molten salt system and a preparation process thereof. SUMMARY

[0003] The present application aims to provide a continuous casting protective slag based on SnO2-Fe2O3 molten salt system and a preparation process thereof to solve the problems raised in the background art.

[0004] To achieve the above-mentioned purpose, on the one hand, the present application provides a continuous casting protective slag based on SnO2-Fe2O3 molten salt system, the mass percentage of the constituent components of which is as follows:

[0005]

[0006]

[0007] The rest is inevitable impurities.

[0008] Among them, the SnO2-Fe2O3 molten salt system is a mixed system composed of SnO2 and Fe2O3. The ionic bond in the system is weaker than the covalent bond, the ionic charge in the two oxides is lower, the interaction between ions is weakened, the cation radius of the two oxides is very close, and the relative molecular mass is small, so that the intermolecular interaction of the system is weak, and the melting point is low.

[0009] As a preferred, the ratio of B2O3 to TiO2 is 1:1.9-3.

[0010] Wherein, [Ti] in the liquid steel can have a redox reaction with B2O3 in the protective slag, and the formula is: 3[Ti] + 2[B2O3] = 3[TiO2] + 4[B]; in order to reduce or prevent the reaction from proceeding, the reactant TiO2 is added to the protective slag. When the TiO2 content in the protective slag is low, O 2- , making the more complex siloxane ion group depolymerize, and the viscosity of the protective slag decreases. When the TiO2 content is high, Ti 4+ is a high-valence ion with a small radius, and its ionic potential is very large, which can capture the anion of the siloxane group, increase the network, and increase the viscosity of the protective slag. At the same time, in the sintering and decarburization process, a small amount of TiO2 is reduced to form TiC, TiN and Ti(CN), which are colloidal high-dispersed solid phases, and have good wettability with molten slag, so the viscosity of the molten slag with high TiO2 content is high. Therefore, the added TiO2 should be in an appropriate amount to reduce the viscosity of the continuous casting protective slag. At the same time, the addition of TiO2 can also reduce the reaction and erosion of the slag liquid and the metal surface, and improve the surface quality of the metal during continuous casting.

[0011] As a preferred, the ratio of CeO2 to B2O3 is 1:0.9-1.2.

[0012] Wherein, B2O3 can well improve the ability of the protective slag to absorb and dissolve CeO2, and the viscosity of the protective slag remains relatively stable after absorbing a large amount of CeO2, but excessive B2O3 in the protective slag may be reduced by C on the steel slag interface during use, causing local boron increase in the steel liquid. When the B2O3 content in the protective slag is too high, the melting temperature of the protective slag is too low, which is not conducive to the heat insulation and heat preservation function of the protective slag.

[0013] In addition, CeO2 and Gd2O3 are both rare earth oxides, and their melting points are relatively low, which can reduce the melting point of the protective slag, improve the dissolution rate and fluidity of the protective slag, thereby promoting the formation of the liquid slag layer, reducing the adhesion and inclusions of the casting blank and the mold wall, and improving the continuous casting efficiency and the quality of the casting blank. They can also act as nucleating agents for the protective slag, promote the formation of crystal nuclei in the protective slag, enhance the crystallization ability of the protective slag, reduce defects such as pores and cracks on the surface of the casting blank, and improve the density and mechanical properties of the casting blank. In addition, Gd2O3 can increase the oxygen solubility of the continuous casting protective slag, which is helpful to remove inclusions in the steel liquid and improve the purity and quality of the casting blank.

[0014] As a preferred, the preparation method of the continuous casting protective slag is as follows:

[0015] S1: weighing the percentage prepared raw materials of the continuous casting protective slag based on the SnO2-Fe2O3 molten salt system, and then grinding;

[0016] S2: After the raw materials in S1 are grinded, the raw materials are stirred and then placed in a mechanical stirring device for stirring and mixing uniformly for standby use;

[0017] S3: The mixed raw materials are placed in a high-temperature smelting furnace for smelting, and the temperature, pH value and smelting time of the mixed system are adjusted to promote the interaction between the particles.

[0018] S4: The smelted substance is reacted and solidified under appropriate temperature conditions, and then the solidified continuous casting protective slag is cooled, grinded and obtained.

[0019] Preferably, the particle size of the grinded particles in S1 is 40-50 nm.

[0020] Preferably, the rotating speed of the mechanical stirring device in S2 is 1200-1400 r / min.

[0021] Preferably, the temperature of the high-temperature smelting furnace in S3 is 1300-1600℃.

[0022] Preferably, the pH value of the mixed system in S3 is 8-10, and the smelting time is 80-100 min.

[0023] Preferably, the solidification temperature of the mixture in S4 is 300-500℃, and the solidification time is 240-600 min.

[0024] Preferably, the grinded particle size in S4 is 180-220 mesh.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] By using SnO2-Fe2O3 molten salt system with low melting point, viscosity and good thermal stability as the base material, adding TiO2 and B2O3 to replace fluoride, not only the harm of fluoride to the environment can be reduced, but also the melting point and viscosity of the continuous casting protective slag can be reduced; the added CeO2 and Gd2O3 can be used as the crystal nucleus agent of the protective slag to promote the formation of crystal nucleus in the protective slag and enhance the crystallization ability of the protective slag, and due to the low melting point, the melting point of the protective slag can be reduced. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application. In the present application, all the equipment and materials can be purchased from the market or commonly used in the industry, and the methods in the following embodiments are conventional methods in the art, unless otherwise specified.

[0028] The following examples in the present application use:

[0029] The cassiterite, hematite, bauxite, feldspar, borax and rutile are purchased from Xi'an Mining Source Nonferrous Metallurgical Research Institute.

[0030] The gadogallite and cerium uraninite are purchased from Tianyue Mineral Gem Co., Ltd.

[0031] The graphite powder is purchased from Henan Hua Xu Graphite Die Co., Ltd.

[0032] The SnO2 is from the raw material cassiterite, the Fe2O3 is from the raw material hematite, the Al2O3 is from the raw material bauxite, the SiO2 is from the raw material feldspar, the Gd2O3 is from the raw material gadogallite, the CeO2 is from the raw material cerium uraninite, the B2O3 is from the raw material borax, the TiO2 is from the raw material rutile, and the C is from the raw material graphite powder.

[0033] Example 1

[0034] In this embodiment, the mass percentage of the constituent components of the continuous casting protective slag based on the SnO2-Fe2O3 molten salt system is as follows:

[0035]

[0036] The preparation method is as follows:

[0037] The required raw materials are weighed and ground to a particle size of 45 nm; after stirring, the raw materials are placed in a mechanical stirring device with a rotating speed of 1300 r / min for uniform mixing; after mixing, the mixture is placed in a high-temperature furnace with a temperature of 1500℃ for smelting, the pH is controlled to be 10, and the smelting time is 80 min; then, the smelted material is solidified at a temperature of 400℃ for 360 min, and the solidified continuous casting protective slag is cooled, ground to a particle size of 200 mesh, and a test sample 1 is obtained.

[0038] Example 2

[0039] In this embodiment, the mass percentage of the constituent components of the continuous casting protective slag based on the SnO2-Fe2O3 molten salt system is as follows:

[0040]

[0041] The preparation method is as follows:

[0042] The required raw materials are weighed and ground to a particle size of 45 nm; after stirring, the raw materials are placed in a mechanical stirring device with a rotating speed of 1300 r / min for uniform stirring; after mixing, the materials are placed in a high-temperature furnace at a temperature of 1500℃ for smelting, with a pH control of 10 and a smelting time of 80 min; then, the smelted material is solidified at a temperature of 400℃ for 360 min, and the solidified continuous casting protective slag is cooled and ground to a particle size of 200 mesh to obtain test sample 2.

[0043] Example 3

[0044] In this example, the mass percentage of the composition of the continuous casting protective slag based on the SnO2-Fe2O3 molten salt system is:

[0045]

[0046]

[0047] The preparation method is as follows:

[0048] The required raw materials are weighed and ground to a particle size of 45 nm; after stirring, the raw materials are placed in a mechanical stirring device with a rotating speed of 1300 r / min for uniform stirring; after mixing, the materials are placed in a high-temperature furnace at a temperature of 1500℃ for smelting, with a pH control of 10 and a smelting time of 80 min; then, the smelted material is solidified at a temperature of 400℃ for 360 min, and the solidified continuous casting protective slag is cooled and ground to a particle size of 200 mesh to obtain test sample 2.

[0049] Example 4

[0050] In this example, the mass percentage of the composition of the continuous casting protective slag based on the SnO2-Fe2O3 molten salt system is:

[0051]

[0052]

[0053] The preparation method is as follows:

[0054] The required raw materials are weighed and ground to a particle size of 45 nm; the raw materials are stirred and then placed in a mechanical stirring device with a rotation speed of 1300 r / min for uniform mixing; after mixing, the materials are placed in a high-temperature furnace at a temperature of 1500°C for smelting, with a pH of 10 and a smelting time of 80 min; then, the smelted material is solidified at a temperature of 400°C for 360 min, and the solidified continuous casting protection slag is cooled and ground to a particle size of 200 mesh to obtain test sample 4.

[0055] Example 5

[0056] In this example, the mass percentage of the composition of the continuous casting protection slag based on the SnO2-Fe2O3 molten salt system is as follows:

[0057]

[0058] The preparation method is as follows:

[0059] The required raw materials are weighed and ground to a particle size of 45 nm; the raw materials are stirred and then placed in a mechanical stirring device with a rotation speed of 1300 r / min for uniform mixing; after mixing, the materials are placed in a high-temperature furnace at a temperature of 1500°C for smelting, with a pH of 10 and a smelting time of 80 min; then, the smelted material is solidified at a temperature of 400°C for 360 min, and the solidified continuous casting protection slag is cooled and ground to a particle size of 200 mesh to obtain test sample 4.

[0060] Comparative Example 1

[0061] The same formulation and preparation process as in Example 1 are used, with the only difference being that B2O3 and TiO2 are replaced with an equal amount of CaF2 to obtain test sample 6.

[0062] Comparative Example 2

[0063] The same formulation and preparation process as in Example 1 are used, with the only difference being that Comparative Example 2 does not contain CeO2 to obtain test sample 7.

[0064] The viscosity and melting temperature of the obtained test samples 1-7 are determined, and the results are shown in the following table:

[0065] Viscosity (Pa s) Melting point (°C) Test sample 1 0.30 1049 Test sample 2 0.31 1091 Test sample 3 0.29 1086 Test sample 4 0.37 1055 Test sample 5 0.34 1059 Test sample 6 0.32 1202 Test sample 7 0.47 1259

[0066] The data in the table above shows that both excessively high and low B2O3 and CeO2 contents affect the viscosity and melting point of the continuous casting protective slag. Comparing the results of samples 1, 2, 3, and 6 reveals that the melting point changes with the B2O3 content, indicating that B2O3 can influence the melting point of the continuous casting protective slag. Comparing the results of samples 3, 4, 5, and 7 shows that the viscosity changes with the CeO2 content. This may be because the viscosity value is related to the melt structure; CeO2 acts as a network modifier in the melt, thus reducing viscosity.

[0067] 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 continuous casting protective slag based on the SnO2-Fe2O3 molten salt system, characterized in that... Its constituent components are expressed as follows: SnO2: 18-38%; Fe2O3: 12-30%; Al2O3: 6-16%; SiO2: 4-16% Gd2O3: 3-7%; CeO2: 4-9%; B2O3: 3-8%; TiO2: 8-20%; C: 1-3%； The rest are unavoidable impurities.

2. The continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 1, characterized in that... The ratio of B2O3 to TiO2 is 1:1.9-3.

3. The continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 1, characterized in that... The ratio of CeO2 to B2O3 is 1:0.9-1.

2.

4. A process for preparing a continuous casting protective slag based on a SnO2-Fe2O3 molten salt system as described in any one of claims 1-3, characterized in that... The preparation method of the continuous casting protective slag is as follows: S1: Weigh the raw materials according to the percentage of the continuous casting protective slag based on the SnO2-Fe2O3 molten salt system as described in any one of claims 1-3, and then grind them; S2: After stirring the raw materials ground in S1, place them in a mechanical stirring device and stir until they are evenly mixed for later use. S3: Place the mixed raw materials in a high-temperature furnace for melting, adjust the temperature and melting time of the mixture to promote the interaction between particles; S4: The smelted material is reacted and solidified under appropriate temperature conditions, and then the solidified mixture is cooled and ground to obtain continuous casting protective slag.

5. The preparation process of continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 4, characterized in that... The grinding particles in S1 have a particle size of 40-50 nm.

6. The preparation process of continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 4, characterized in that... The mechanical stirring device in S2 has a rotation speed of 1200-1400 r / min.

7. The preparation process of continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 4, characterized in that... The temperature of the high-temperature furnace in S3 is 1300-1600℃.

8. The preparation process of continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 4, characterized in that... The melting time for the mixed system in S3 is 80-100 min.

9. The preparation process of continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 4, characterized in that... The curing temperature of the mixture in S4 is 300-500℃; the curing time is 240-600 min.

10. The preparation process of continuous casting protective slag based on the SnO2-Fe2O3 molten salt system according to claim 4, characterized in that... The grinding particle size in S4 is 180-220 mesh.

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