Low-reactivity Al-Ti inhibition type casting powder for continuous casting based on pre-melted hollow particles and preparation process of low-reactivity Al-Ti inhibition type casting powder

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to low-reactivity Al-Ti inhibition type casting powder for continuous casting based on premelted hollow particles and a preparation technology of the low-reactivity Al-Ti inhibition type casting powder. Wherein the water-quenched melt particles comprise an Al-Ti inhibitor, a melt, aluminum oxide short fibers and carbon black, pre-sintered aluminum oxide and titanium dioxide serve as the Al-Ti inhibitor, a stable Al-Ti-O network structure is formed in the melt, the reaction activity of the slag and the high-activity Al-Ti molten steel is effectively reduced, the aluminum oxide short fibers are introduced to form an enhanced network, and the high-activity Al-Ti molten steel is obtained. According to the casting powder, nano silicon carbide and boron carbide are matched to form synergistic reinforcement, ethyl silicate hydrolysate, water glass and sodium carboxymethyl cellulose are adopted to construct a dual-bonding system, the casting powder of the hollow structure is prepared, and the mechanical strength of the casting powder is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and in particular to a low-reactivity Al-Ti inhibitory mold powder for continuous casting based on pre-melted hollow particles and a preparation process thereof. Background Art

[0002] In the continuous casting process of iron and steel, as a key functional material, the performance of the mold powder directly affects the surface quality of the casting billet, the internal cleanliness and the stability of continuous casting production. Traditional continuous casting mold powders are mostly based on silicate-carbonate systems, and achieve lubrication and heat insulation functions by regulating the melting speed, viscosity and crystallization characteristics. For example, the hollow spherical particle mold powder has the advantages of good spreading property, strong air permeability and no caking, and thus has received extensive attention. However, the existing mold powders of hollow particles are easy to break during transportation or use, and such overly fine particles form aggregates due to electrostatic or surface energy effects, reducing the fluidity of the slag material, resulting in the inability to spread evenly on the molten steel surface, forming a discontinuous protective layer, making the molten steel surface more easily oxidized and increasing the generation of inclusions. In view of this, we propose a low-reactivity Al-Ti inhibitory mold powder for continuous casting based on pre-melted hollow particles and a preparation process thereof. Summary of the Invention

[0003] The purpose of the present invention is to provide a low-reactivity Al-Ti inhibitory mold powder for continuous casting based on pre-melted hollow particles and a preparation process thereof to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides a low-reactivity Al-Ti inhibitory mold powder for continuous casting based on pre-melted hollow particles, and the mold powder includes water-quenched melt particles, a composite binder and ethyl silicate hydrolyzate;

[0005] Among them, the water-quenched melt particles include an Al-Ti inhibitor, a melt, alumina short fibers and carbon black.

[0006] Introduce nano silicon carbide (SiC) and boron carbide into the melt , using its high hardness property to fill the micropores inside the hollow particles, inhibit crack propagation, enhance the strength of the particle skeleton, pre-sinter alumina (Al2O3) and titanium dioxide (TiO2) into the stable phase of aluminum titanate (Al2TiO5) spinel and Al-Ti solid solution, inhibit the reaction of Al and Ti elements in the molten steel, reduce the reactivity between the mold powder and the molten steel, and reduce the generation of inclusions. Add alumina short fibers and carbon black during the water quenching stage. On the one hand, use the alumina short fibers to form a reinforcing skeleton that penetrates the hollow particles to enhance the particle structure. On the other hand, use the synergistic effect of carbon black and the Al-Ti inhibitor to reduce the oxidizability of the molten steel. Adopt a composite system of sodium silicate and sodium carboxymethylcellulose to form a three-dimensional network cross-linked structure, which provides plasticity together during the slurry mixing and drying stages to prevent particle cracking. At the same time, incorporate the hydrolyzate of tetraethyl orthosilicate to generate nano-SiO2 gel, which wraps the particle surface to form a protective film and enhance the particle strength. In the later sintering stage, first preheat to slowly remove the residual organic matter sodium carboxymethylcellulose to avoid particle rupture caused by rapid heating, and heat up to 800 - 850 °C to promote partial remelting of the melt, realize surface micro-melting of the particles, make up for the strength loss after the decomposition of sodium carboxymethylcellulose, the sodium silicate gradually transforms into a silicate glass phase, and the SiO2 gel is sintered and densified at high temperature to further enhance the particle density and strengthen the mechanical strength of the hollow structure.

[0007] On the other hand, the present invention provides a preparation process for a low-reactivity Al-Ti inhibiting mold powder for continuous casting based on pre-melted hollow particles, which is used for the low-reactivity Al-Ti inhibiting mold powder for continuous casting based on pre-melted hollow particles described in any one of the above, and includes the following steps:

[0008] Mix alumina and titanium dioxide and then press them into compacts. The forming pressure is 50 - 150 MPa, and the pressure holding time is 1 - 3 min. Then pre-sinter at 1300 - 1400 °C for 2 - 4 h and ball mill to obtain the Al-Ti inhibitor;

[0009] Add calcium oxide, silicon dioxide, alumina, magnesia, zirconia, sodium oxide, calcium fluoride, and lithium carbonate to an electric arc furnace, heat up to 1550 - 1600 °C, introduce argon with a flow rate of 1 - 2 L / min, stir at 200 - 300 rpm and melt for 30 - 40 min, cool down to 1400 - 1450 °C, add the Al-Ti inhibitor, nano-silicon carbide, and boron carbide, and keep warm for 20 - 30 min to obtain a melt;

[0010] Inject the melt into a high-pressure water atomization system at a flow rate of 0.3 - 0.5 kg / min, and simultaneously add alumina short fibers and carbon black to form water-quenched melt particles;

[0011] Mix the water-quenched melt particles, composite binder, and hydrolyzate of tetraethyl orthosilicate to obtain a slurry, and dry the slurry with a centrifugal spray dryer to obtain hollow particles;

[0012] After keeping the hollow particles at 400 - 500 °C for 20 - 30 min, heat them to 800 - 850 °C at a rate of 10 °C / min in a tunnel furnace and keep them at this temperature for 8 - 10 min to obtain a low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles.

[0013] The staged heating at 400 - 500 °C and 800 - 850 °C in the sintering process helps the full decomposition of the organic substance sodium carboxymethyl cellulose and reduces the residue of free sodium ions.

[0014] Preferably, the mass ratio of alumina to titanium dioxide is 6 - 7:3.5.

[0015] Preferably, the particle size range of the Al-Ti inhibitor is 5 - 10 μm.

[0016] Preferably, there are 23.7 - 29.5 parts by weight of calcium oxide, 23.5 - 29.2 parts by weight of silica, 11.8 - 14.7 parts by weight of alumina, 3.4 - 5.2 parts by weight of magnesia, 2.2 - 4.8 parts by weight of zirconia, 1.2 - 1.5 parts by weight of sodium oxide, 3.3 - 5.6 parts by weight of calcium fluoride, 1.6 - 2 parts by weight of lithium carbonate, 4.5 - 8.3 parts by weight of Al-Ti inhibitor, 0.4 - 0.9 parts by weight of nano silicon carbide, 0.3 - 0.6 parts by weight of boron carbide, 1.7 - 3.5 parts by weight of alumina short fibers, 1.5 - 2.1 parts by weight of carbon black, 6.2 - 8.4 parts by weight of composite binder, 10.6 - 12.8 parts by weight of ethyl silicate hydrolysis solution; among them, the length range of the alumina short fibers is 100 - 200 μm.

[0017] Preferably, the pressure of the high-pressure water atomization system is 8 - 10 MPa and the water temperature is 18 - 22 °C.

[0018] Preferably, the ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9 - 1.1:3 - 4:1, with a pH of 3 - 4, and its acidic environment helps to promote the partial dissolution and transformation of sodium ions.

[0019] Preferably, the composite binder is obtained from water glass and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the degree of substitution of sodium carboxymethyl cellulose is 0.6 - 0.8.

[0020] Preferably, the inlet temperature of the centrifugal spray dryer is 250 - 255 °C and the outlet temperature is 90 - 95 °C.

[0021] Preferably, the particle size range of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles is 0.6 - 0.8 mm.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] In the low-reactivity Al-Ti inhibitory mold flux for continuous casting based on pre-melted hollow particles and its preparation process, a dual strengthening mechanism of "fiber reinforcement + nano-dispersion" is formed by introducing alumina short fibers, nano-silicon carbide, and boron carbide. The alumina short fibers enhance the particle toughness through physical interpenetration, the nano-silicon carbide fills the pores and strengthens the grain boundaries, improving the compressive strength of the hollow particles, effectively solving the problem of powdering caused by mechanical impact during transportation and use. The Al-Ti inhibitor prepared by pre-sintering is uniformly dispersed in the melt during the melting stage, inhibiting the oxidation reaction of Al and Ti elements in the molten steel, reducing the interfacial activity between the mold flux and the molten steel, and reducing the generation of inclusions. Combined with the dual bonding network of the composite binder and the hydrolyzate of ethyl silicate, the composite binder provides plasticity in the early stage to prevent particle cracking, and in the later stage, it promotes the formation of a dense nano-SiO2 layer from the hydrolyzate of ethyl silicate, ensuring the structural stability of the particles during drying and heat treatment, achieving the unity of low stability and high mechanical strength of the mold flux, and solving the problem of increased inclusions caused by the too fine particle size of traditional hollow mold fluxes. Specific embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of 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.

[0025] The low-reactivity Al-Ti inhibitory mold flux for continuous casting based on pre-melted hollow particles of the present invention, the mold flux includes water-quenched melt particles, a composite binder, and a hydrolyzate of ethyl silicate;

[0026] Among them, the water-quenched melt particles include an Al-Ti inhibitor, a melt, alumina short fibers, and carbon black.

[0027] Example 1: A low-reactivity Al-Ti inhibitory mold flux for continuous casting based on pre-melted hollow particles and its preparation process, including the following steps:

[0028] The mold flux includes water-quenched melt particles, a composite binder, and a hydrolyzate of ethyl silicate; among them, the water-quenched melt particles include an Al-Ti inhibitor, a melt, alumina short fibers, and carbon black;

[0029] The mass ratio of alumina to titanium dioxide is 6:3.5; 23.7 parts by weight of calcium oxide, 23.5 parts by weight of silicon dioxide, 11.8 parts by weight of alumina, 3.4 parts by weight of magnesium oxide, 2.2 parts by weight of zirconium dioxide, 1.2 parts by weight of sodium oxide, 3.3 parts by weight of calcium fluoride, 1.6 parts by weight of lithium carbonate, 4.5 parts by weight of Al-Ti inhibitor, 0.4 parts by weight of nano silicon carbide, 0.3 parts by weight of boron carbide, 1.7 parts by weight of alumina short fibers, 1.5 parts by weight of carbon black, 6.2 parts by weight of composite binder, 10.6 parts by weight of ethyl silicate hydrolysis solution; the ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9:3:1, and the pH is 3; the composite binder is obtained from water glass and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the degree of substitution of sodium carboxymethyl cellulose is 0.7;

[0030] Mix alumina and titanium dioxide and then press them into a green compact. The forming pressure is 150 MPa, and the pressure holding time is 1 min. Then pre-sinter at 1300 °C for 4 h and ball mill to obtain an Al-Ti inhibitor with a particle size range of 5 μm;

[0031] Add calcium oxide, silicon dioxide, alumina, magnesium oxide, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate into an electric arc furnace, heat up to 1600 °C, introduce argon with a flow rate of 2 L / min, stir at 300 rpm for 30 min, cool down to 1450 °C, add the Al-Ti inhibitor, nano silicon carbide and boron carbide, and keep warm for 30 min to obtain a melt;

[0032] Inject the melt into a high-pressure water atomization system at a flow rate of 0.5 kg / min, with a pressure of 10 MPa and a water temperature of 22 °C, and simultaneously add alumina short fibers and carbon black to form water-quenched melt particles;

[0033] Mix the water-quenched melt particles, composite binder, and ethyl silicate hydrolysis solution to obtain a slurry. Dry the slurry in a centrifugal spray dryer with an inlet temperature of 250 °C and an outlet temperature of 90 °C to obtain hollow particles;

[0034] After keeping the hollow particles at 400 °C for 30 min, heat them in a tunnel furnace from 400 °C to 850 °C at a rate of 10 °C / min and keep warm for 10 min to obtain a low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles with a particle size range of 0.8 mm.

[0035] Example 2: A low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles and its preparation process, including the following steps:

[0036] The mold powder includes water-quenched melt particles, composite binder and ethyl silicate hydrolysis solution; among them, the water-quenched melt particles include Al-Ti inhibitor, melt, alumina short fibers and carbon black;

[0037] The mass ratio of alumina to titanium dioxide is 6:3.5; 23.7 parts by weight of calcium oxide, 23.5 parts by weight of silicon dioxide, 11.8 parts by weight of alumina, 3.4 parts by weight of magnesium oxide, 2.2 parts by weight of zirconium dioxide, 1.2 parts by weight of sodium oxide, 3.3 parts by weight of calcium fluoride, 1.6 parts by weight of lithium carbonate, 4.5 parts by weight of Al-Ti inhibitor, 0.65 parts by weight of nano silicon carbide, 0.45 parts by weight of boron carbide, 2.6 parts by weight of alumina short fiber, 1.5 parts by weight of carbon black, 6.2 parts by weight of composite binder, 10.6 parts by weight of ethyl silicate hydrolysis solution; the ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9:3:1, and the pH is 3; the composite binder is obtained from sodium silicate and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the degree of substitution of sodium carboxymethyl cellulose is 0.7;

[0038] Mix alumina and titanium dioxide and then press them into a blank. The forming pressure is 150 MPa, and the pressure holding time is 1 min. Then pre-sinter at 1300 °C for 4 h and ball mill to obtain an Al-Ti inhibitor with a particle size range of 5 μm;

[0039] Add calcium oxide, silicon dioxide, alumina, magnesium oxide, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate into an electric arc furnace, heat up to 1600 °C, introduce argon with a flow rate of 2 L / min, stir at 300 rpm for 30 min, cool down to 1450 °C, add the Al-Ti inhibitor, nano silicon carbide and boron carbide, and keep warm for 30 min to obtain a melt;

[0040] Inject the melt into a high-pressure water atomization system at a flow rate of 0.5 kg / min, with a pressure of 10 MPa and a water temperature of 22 °C, and simultaneously add alumina short fiber and carbon black to form water-quenched melt particles;

[0041] Mix the water-quenched melt particles, composite binder, and ethyl silicate hydrolysis solution to obtain a slurry, and dry the slurry with a centrifugal spray dryer. The inlet temperature is 250 °C, and the outlet temperature is 90 °C to obtain hollow particles;

[0042] After keeping the hollow particles at 400 °C for 30 min, heat them up to 850 °C at a rate of 10 °C / min in a tunnel furnace and keep warm for 10 min to obtain a low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles with a particle size range of 0.8 mm.

[0043] Example 3: A low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles and its preparation process, including the following steps:

[0044] The mold powder includes water-quenched melt particles, composite binder and ethyl silicate hydrolysis solution; among them, the water-quenched melt particles include Al-Ti inhibitor, melt, alumina short fiber and carbon black;

[0045] The mass ratio of alumina to titanium dioxide is 6:3.5; 23.7 parts by weight of calcium oxide, 23.5 parts by weight of silicon dioxide, 11.8 parts by weight of alumina, 3.4 parts by weight of magnesium oxide, 2.2 parts by weight of zirconium dioxide, 1.2 parts by weight of sodium oxide, 3.3 parts by weight of calcium fluoride, 1.6 parts by weight of lithium carbonate, 4.5 parts by weight of Al-Ti inhibitor, 0.9 parts by weight of nano silicon carbide, 0.6 parts by weight of boron carbide, 3.5 parts by weight of alumina short fibers, 1.5 parts by weight of carbon black, 6.2 parts by weight of composite binder, 10.6 parts by weight of ethyl silicate hydrolysis solution; the ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9:3:1, and the pH is 3; the composite binder is obtained from water glass and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the substitution degree of sodium carboxymethyl cellulose is 0.7;

[0046] Mix alumina and titanium dioxide and then press them into a green compact. The forming pressure is 150 MPa, and the pressure holding time is 1 min. Then pre-sinter at 1300 °C for 4 h and ball mill to obtain an Al-Ti inhibitor with a particle size range of 5 μm;

[0047] Add calcium oxide, silicon dioxide, alumina, magnesium oxide, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate into an electric arc furnace. Heat up to 1600 °C, introduce argon with a flow rate of 2 L / min, stir at 300 rpm for 30 min, cool down to 1450 °C, add the Al-Ti inhibitor, nano silicon carbide and boron carbide, and keep warm for 30 min to obtain a melt;

[0048] Inject the melt into a high-pressure water atomization system at a flow rate of 0.5 kg / min. The pressure is 10 MPa, and the water temperature is 22 °C. Synchronously add alumina short fibers and carbon black to form water-quenched melt particles;

[0049] Mix the water-quenched melt particles, composite binder, and ethyl silicate hydrolysis solution to obtain a slurry. Dry the slurry in a centrifugal spray dryer with an inlet temperature of 250 °C and an outlet temperature of 90 °C to obtain hollow particles;

[0050] After keeping the hollow particles at 400 °C for 30 min, heat them up to 850 °C at a rate of 10 °C / min in a tunnel furnace and keep warm for 10 min to obtain a low-reactivity Al-Ti inhibited mold powder for continuous casting with a particle size range of 0.8 mm based on pre-melted hollow particles.

[0051] Example 4: A low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles and its preparation process, including the following steps:

[0052] The mold powder includes water-quenched melt particles, composite binder and ethyl silicate hydrolysis solution; among them, the water-quenched melt particles include Al-Ti inhibitor, melt, alumina short fibers and carbon black;

[0053] The mass ratio of alumina to titanium dioxide is 6:3.5; 23.7 parts by weight of calcium oxide, 23.5 parts by weight of silicon dioxide, 11.8 parts by weight of alumina, 3.4 parts by weight of magnesium oxide, 2.2 parts by weight of zirconium dioxide, 1.2 parts by weight of sodium oxide, 3.3 parts by weight of calcium fluoride, 1.6 parts by weight of lithium carbonate, 4.5 parts by weight of Al-Ti inhibitor, 0.65 parts by weight of nano silicon carbide, 0.45 parts by weight of boron carbide, 2.6 parts by weight of alumina short fibers, 1.5 parts by weight of carbon black, 7.3 parts by weight of composite binder, 11.7 parts by weight of ethyl silicate hydrolysis solution; the ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9:3:1, and the pH is 3; the composite binder is obtained from sodium silicate and sodium carboxymethylcellulose in a mass ratio of 3:1, and the degree of substitution of sodium carboxymethylcellulose is 0.7;

[0054] Mix alumina and titanium dioxide and then press them into a green compact. The forming pressure is 150 MPa, and the pressure holding time is 1 min. Then pre-sinter at 1300 °C for 4 h and ball mill to obtain an Al-Ti inhibitor with a particle size range of 5 μm;

[0055] Add calcium oxide, silicon dioxide, alumina, magnesium oxide, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate into an electric arc furnace. Heat up to 1600 °C, introduce argon with a flow rate of 2 L / min, stir at 300 rpm for 30 min, cool down to 1450 °C, add the Al-Ti inhibitor, nano silicon carbide and boron carbide, and keep warm for 30 min to obtain a melt;

[0056] Inject the melt into a high-pressure water atomization system at a flow rate of 0.5 kg / min, with a pressure of 10 MPa and a water temperature of 22 °C. Synchronously add alumina short fibers and carbon black to form water-quenched melt particles;

[0057] Mix the water-quenched melt particles, composite binder, and ethyl silicate hydrolysis solution to obtain a slurry. Dry the slurry in a centrifugal spray dryer with an inlet temperature of 250 °C and an outlet temperature of 90 °C to obtain hollow particles;

[0058] After keeping the hollow particles at 400 °C for 30 min, heat them up to 850 °C at a rate of 10 °C / min in a tunnel furnace and keep warm for 10 min to obtain a low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles with a particle size range of 0.8 mm.

[0059] Example 5: A low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles and its preparation process, including the following steps:

[0060] The mold powder includes water-quenched melt particles, composite binder and ethyl silicate hydrolysis solution; among them, the water-quenched melt particles include Al-Ti inhibitor, melt, alumina short fibers and carbon black;

[0061] The mass ratio of alumina to titanium dioxide is 6:3.5; 23.7 parts by weight of calcium oxide, 23.5 parts by weight of silicon dioxide, 11.8 parts by weight of alumina, 3.4 parts by weight of magnesium oxide, 2.2 parts by weight of zirconium dioxide, 1.2 parts by weight of sodium oxide, 3.3 parts by weight of calcium fluoride, 1.6 parts by weight of lithium carbonate, 4.5 parts by weight of Al-Ti inhibitor, 0.65 parts by weight of nano silicon carbide, 0.45 parts by weight of boron carbide, 2.6 parts by weight of alumina short fiber, 1.5 parts by weight of carbon black, 8.4 parts by weight of composite binder, 12.8 parts by weight of ethyl silicate hydrolyzate; the ethyl silicate hydrolyzate is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9:3:1, and the pH is 3; the composite binder is obtained from sodium silicate and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the substitution degree of sodium carboxymethyl cellulose is 0.7;

[0062] Mix alumina and titanium dioxide and then press them into a blank. The forming pressure is 150 MPa, and the pressure holding time is 1 min. Then pre-sinter at 1300 °C for 4 h and ball mill to obtain an Al-Ti inhibitor with a particle size range of 5 μm;

[0063] Add calcium oxide, silicon dioxide, alumina, magnesium oxide, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate into an electric arc furnace, heat up to 1600 °C, introduce argon with a flow rate of 2 L / min, stir at 300 rpm for 30 min, cool down to 1450 °C, add the Al-Ti inhibitor, nano silicon carbide and boron carbide, and keep warm for 30 min to obtain a melt;

[0064] Inject the melt into a high-pressure water atomization system at a flow rate of 0.5 kg / min, with a pressure of 10 MPa and a water temperature of 22 °C, and simultaneously add alumina short fiber and carbon black to form water-quenched melt particles;

[0065] Mix the water-quenched melt particles, composite binder, and ethyl silicate hydrolyzate to obtain a slurry, and dry the slurry in a centrifugal spray dryer with an inlet temperature of 250 °C and an outlet temperature of 90 °C to obtain hollow particles;

[0066] After keeping the hollow particles at 400 °C for 30 min, heat them in a tunnel furnace from 400 °C to 850 °C at a rate of 10 °C / min and keep warm for 10 min to obtain a low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles with a particle size range of 0.8 mm.

[0067] Example 6: A low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles and its preparation process, including the following steps:

[0068] The mold powder includes water-quenched melt particles, composite binder and ethyl silicate hydrolyzate; among them, the water-quenched melt particles include Al-Ti inhibitor, melt, alumina short fiber and carbon black;

[0069] The mass ratio of alumina to titanium dioxide is 6:3.5; 23.7 parts by weight of calcium oxide, 23.5 parts by weight of silicon dioxide, 11.8 parts by weight of alumina, 3.4 parts by weight of magnesium oxide, 2.2 parts by weight of zirconium dioxide, 1.2 parts by weight of sodium oxide, 3.3 parts by weight of calcium fluoride, 1.6 parts by weight of lithium carbonate, 4.5 parts by weight of Al-Ti inhibitor, 0.65 parts by weight of nano silicon carbide, 0.45 parts by weight of boron carbide, 2.6 parts by weight of alumina short fiber, 1.5 parts by weight of carbon black, 8.4 parts by weight of composite binder, 12.8 parts by weight of ethyl silicate hydrolysis solution; the ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9:3:1, and the pH is 3; the composite binder is obtained from water glass and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the degree of substitution of sodium carboxymethyl cellulose is 0.2;

[0070] Mix alumina and titanium dioxide and then press them into a green compact. The forming pressure is 150 MPa, and the pressure holding time is 1 min. Then pre-sinter at 1300 °C for 4 h and ball mill to obtain an Al-Ti inhibitor with a particle size range of 5 μm;

[0071] Add calcium oxide, silicon dioxide, alumina, magnesium oxide, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate into an electric arc furnace. Heat up to 1600 °C, introduce argon with a flow rate of 2 L / min, stir at 300 rpm for 30 min, cool down to 1450 °C, add the Al-Ti inhibitor, nano silicon carbide and boron carbide, and keep warm for 30 min to obtain a melt;

[0072] Inject the melt into a high-pressure water atomization system at a flow rate of 0.5 kg / min. The pressure is 10 MPa, and the water temperature is 22 °C. Synchronously add alumina short fiber and carbon black to form water-quenched melt particles;

[0073] Mix the water-quenched melt particles, composite binder, and ethyl silicate hydrolysis solution to obtain a slurry. Dry the slurry in a centrifugal spray dryer. The inlet temperature is 250 °C, and the outlet temperature is 90 °C to obtain hollow particles;

[0074] After keeping the hollow particles at 400 °C for 30 min, heat them up to 850 °C at a rate of 10 °C / min in a tunnel furnace and keep warm for 10 min to obtain a low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles with a particle size range of 0.8 mm.

[0075] Example 7: A low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles and its preparation process, including the following steps:

[0076] The mold powder includes water-quenched melt particles, composite binder and ethyl silicate hydrolysis solution; among them, the water-quenched melt particles include Al-Ti inhibitor, melt, alumina short fiber and carbon black;

[0077] The mass ratio of alumina to titanium dioxide is 6:3.5; 23.7 parts by weight of calcium oxide, 23.5 parts by weight of silicon dioxide, 11.8 parts by weight of alumina, 3.4 parts by weight of magnesium oxide, 2.2 parts by weight of zirconium dioxide, 1.2 parts by weight of sodium oxide, 3.3 parts by weight of calcium fluoride, 1.6 parts by weight of lithium carbonate, 4.5 parts by weight of Al-Ti inhibitor, 0.65 parts by weight of nano silicon carbide, 0.45 parts by weight of boron carbide, 2.6 parts by weight of alumina short fiber, 1.5 parts by weight of carbon black, 8.4 parts by weight of composite binder, 12.8 parts by weight of ethyl silicate hydrolysis solution; the ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol and water in a mass ratio of 0.9:3:1, and the pH is 3; the composite binder is obtained from sodium silicate and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the substitution degree of sodium carboxymethyl cellulose is 1.5;

[0078] Mix alumina and titanium dioxide and then press them into a green compact. The forming pressure is 150 MPa and the pressure holding time is 1 min. Then pre-sinter at 1300 °C for 4 h and ball mill to obtain an Al-Ti inhibitor with a particle size range of 5 μm;

[0079] Add calcium oxide, silicon dioxide, alumina, magnesium oxide, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate into an electric arc furnace. Heat up to 1600 °C, introduce argon with a flow rate of 2 L / min, stir at 300 rpm for 30 min, cool down to 1450 °C, add the Al-Ti inhibitor, nano silicon carbide, and boron carbide, and keep warm for 30 min to obtain a melt;

[0080] Inject the melt into a high-pressure water atomization system at a flow rate of 0.5 kg / min. The pressure is 10 MPa and the water temperature is 22 °C. Synchronously add alumina short fiber and carbon black to form water-quenched melt particles;

[0081] Mix the water-quenched melt particles, composite binder, and ethyl silicate hydrolysis solution to obtain a slurry. Dry the slurry in a centrifugal spray dryer with an inlet temperature of 250 °C and an outlet temperature of 90 °C to obtain hollow particles;

[0082] After keeping the hollow particles at 400 °C for 30 min, heat them up to 850 °C at a rate of 10 °C / min in a tunnel furnace and keep warm for 10 min to obtain a low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles with a particle size range of 0.8 mm.

[0083] Comparative Example 1: Using the method of Example 5, without adding nano silicon carbide, boron carbide, and alumina short fiber.

[0084] Comparative Example 2: Using the method of Example 5, using a composite binder but without adding ethyl silicate hydrolysis solution.

[0085] Comparative Example 3: Using the method of Example 5, alumina and titanium dioxide were directly added, and the Al-Ti inhibitor was not prepared by pre-sintering.

[0086] Comparative Example 4: Using the method of Example 5, the low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles prepared was crushed to a particle size of 0.1 mm.

[0087] The low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles prepared by using nano-silicon carbide, boron carbide and alumina short fibers in the present invention, wherein, the inspection items and inspection standards of the performance indexes of the mold powder are as follows:

[0088] Compressive strength (MPa), which reflects the ability of the mold powder particles to resist external force damage and directly affects the structural integrity during transportation and use. A compressive strength > 15 MPa can ensure that the particles do not break during continuous casting, avoiding the generation of fine powder inclusions. Take the complete hollow particle mold powder, fix it in a cylindrical mold (Φ10 mm × 10 mm) with epoxy resin, polish it to a surface roughness Ra < 1 μm after curing, and through a universal material testing machine, with a loading rate of 1 mm / min, test and record the maximum load when the particles break;

[0089] The pulverization rate (%) is used to quantify the proportion of fine powder generated by mechanical impact of the mold powder particles during transportation or use, which is directly related to the inclusion risk. Take 50 g of the sample and screen out the existing fine powder (< 0.2 mm), simulate transportation vibration impact through a free-fall testing machine, with a drop height of 1 m and 50 drop times, test the mass difference of the particles before and after, and the pulverization rate (%) = fine powder mass (< 0.2 mm) / initial mass × 100%;

[0090] The inclusion adsorption efficiency reflects the ability of the mold powder to capture inclusions in the molten steel and directly affects the quality of the cast slab. Take a molten steel sample containing non-metallic inclusions, simulate the continuous casting temperature in a high-temperature test furnace, keep it at 1600 °C for 30 min, observe the number of inclusions on the surface of the mold powder, and calculate the inclusion adsorption efficiency (%) = (1 - inclusion content after treatment / initial inclusion content) × 100%. The inclusion adsorption efficiency (%) greater than 85% is qualified.

[0091] Through the above standards, the low-reactivity Al-Ti inhibited mold powder for continuous casting based on pre-melted hollow particles prepared in the above Examples 1-7 and Comparative Examples 1-4 was tested, and the obtained data are shown in Table 1:

[0092] Table 1 Performance data of Examples 1-7 and Comparative Examples 1-4

[0093] The above data fully show that, compared with Comparative Examples 1-4, in Examples 1-7, it can be clearly seen the effects of nano silicon carbide, boron carbide and alumina short fibers on the mechanical properties, anti-pulverization property and inclusion adsorption efficiency of the mold powder.

[0094] Since the present invention uses nano silicon carbide, boron carbide and alumina short fibers to prepare the mold powder, the properties of the mold powder are effectively improved as follows:

[0095] It can be seen from Examples 1-3 that as the contents of nano silicon carbide, boron carbide and alumina short fibers increase continuously, the mechanical properties, anti-pulverization property and inclusion adsorption efficiency of the mold powder increase first and then decrease. Nano silicon carbide and boron carbide form a pinning effect to hinder crack propagation. At the same time, alumina short fibers form a three-dimensional network through physical interpenetration and chemical bonding to absorb impact energy. Therefore, through the synergistic effect of nano silicon carbide, boron carbide and alumina short fibers, the mechanical properties of the hollow particles are improved. However, excessive nano silicon carbide, boron carbide and alumina short fibers will cause stress concentration due to nanoparticle agglomeration, a decrease in interfacial bonding strength, and hinder the melt flow, resulting in a decline in mechanical properties, and further affecting the anti-pulverization property to also decrease. The high specific surface area of nano silicon carbide and boron carbide provides more active adsorption sites, and the alumina short fibers form a porous network structure, increasing the contact area between the molten slag and the molten steel. Therefore, the inclusion adsorption efficiency increases first. However, excessive nano silicon carbide, boron carbide and alumina short fibers will cause an increase in the viscosity of the molten slag, a decrease in fluidity, and hinder the floating and adsorption of inclusions, resulting in a decrease in the inclusion adsorption efficiency.

[0096] It can be seen from Examples 2, 4 and 5 that as the contents of the composite binder and ethyl silicate hydrolysis solution increase continuously, the mechanical properties, anti-pulverization property and inclusion adsorption efficiency of the mold powder continuously increase. Sodium silicate and sodium carboxymethylcellulose form a cross-linked network in the drying stage to fill the particle gaps and inhibit drying shrinkage cracking. The flexibility of sodium carboxymethylcellulose provides a temporary skeleton support during drying to reduce stress concentration inside the particles. The nano-SiO2 gel generated by the hydrolysis of ethyl silicate covers the particle surface and fills the internal micropores of the particles, filling the micro-defects and forming a dense protective layer to improve the surface hardness and compressive strength of the particles. At high temperatures, sodium silicate is transformed into a silicate glass phase, and nano-SiO2 reacts with the matrix to generate a high-melting-point silicate phase, further strengthening the particle skeleton. Therefore, the mechanical properties and anti-pulverization property gradually increase. Since the fine particles generated by self-pulverization gradually decrease, the formation of aggregates is effectively avoided. Moreover, the active SiO2 network formed by the ethyl silicate hydrolysis solution can further enhance the chemical adsorption of inclusions, resulting in a gradual increase in the inclusion adsorption efficiency.

[0097] It can be seen from Examples 5-7 that as the degree of substitution of sodium carboxymethylcellulose changes continuously, the mechanical properties, anti-pulverization property and inclusion adsorption efficiency of the mold powder change continuously. At low degrees of substitution, the number of carboxymethyl groups in sodium carboxymethylcellulose is insufficient, resulting in poor water solubility and dispersibility, making it difficult to form a uniform bonding phase with sodium silicate, and the bonding force is insufficient, and the combination between particles is loose, resulting in low mechanical strength and anti-pulverization property of the mold powder. Moreover, the poor dispersibility of sodium carboxymethylcellulose also affects the overall distribution of the mold powder structure, thereby affecting the inclusion adsorption efficiency. At high degrees of substitution, the molecular chain rigidity increases and the flexibility decreases, and the shrinkage stress increases during drying, which is prone to cause microcracks, instead reducing the mechanical strength and anti-pulverization property of the mold powder, and the residual organic matter increases, making the viscosity of the mold powder increase, hindering the floating and adsorption of inclusions, and the inclusion adsorption efficiency decreases.

[0098] According to the above test experiments, it can be known that the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles prepared in Example 5 has the optimal performance, so Example 5 is taken as the optimal example;

[0099] It can be seen from the comparison between Example 5 and Comparative Examples 1-4:

[0100] In Comparative Example 1, nano silicon carbide, boron carbide and alumina short fibers were not added, and the mechanical properties, anti-pulverization property and inclusion adsorption efficiency of the mold powder were worse. Nano silicon carbide and boron carbide, as rigid reinforcement phases, were originally embedded in the matrix through the "pinning effect" to hinder dislocation movement and crack propagation. Alumina short fibers penetrated the hollow structure to form a reinforcing skeleton. Therefore, when nano silicon carbide, boron carbide and alumina short fibers are missing, the mechanical strength and anti-pulverization property decrease significantly, and without alumina short fibers, the porous network structure formed by alumina short fibers is also missing, so the inclusion adsorption efficiency is limited.

[0101] In Comparative Example 2, a composite binder was used, but ethyl silicate hydrolyzate was not added, and the mechanical properties, anti-pulverization property and inclusion adsorption efficiency of the mold powder were worse. The nano-SiO2 generated by ethyl silicate hydrolyzate can not only fill the internal pores of the particles, reduce the stress concentration points, but also react with sodium silicate in the composite binder to form silicon-oxygen bonds, strengthening the interfacial bonding between particles. The mechanical properties and anti-pulverization properties decrease, and the surface activity of nano-SiO2 is high, which can promote the adsorption of inclusions. Therefore, the mechanical properties, anti-pulverization property and inclusion adsorption efficiency of the mold powder decrease significantly.

[0102] In Comparative Example 3, alumina and titanium dioxide were directly added without preparing the Al-Ti inhibitor through pre-sintering. As a result, the mechanical properties, anti-pulverization property, and inclusion adsorption efficiency of the mold flux were poorer. The unpre-sintered alumina and titanium dioxide were difficult to disperse uniformly in the melt, and the direct reaction process between the two was insufficient, resulting in the formation of hard inclusions in the locally alumina- and titanium dioxide-rich regions, triggering internal stress concentration and microcracks. Moreover, due to the formation of Al-Ti-rich active sites on the surface of the Al-Ti inhibitor through pre-sintering, it could react with the free oxygen in the molten steel to form a low-melting-point phase, promoting inclusion adsorption. However, relying solely on physical adsorption, the surface chemical activity was insufficient and the efficiency was low. Therefore, the mechanical properties, anti-pulverization property, and inclusion adsorption efficiency of the mold flux decreased significantly.

[0103] In Comparative Example 4, the prepared low-reactivity Al-Ti inhibited mold flux based on pre-melted hollow particles was crushed to a particle size of 0.1 mm. Since the particle size of the mold flux was too fine, it was easy to form aggregates, reducing the fluidity of the slag material and resulting in the inability to spread evenly on the surface of the molten steel, forming a discontinuous protective layer. The discontinuous protective layer could not effectively isolate the air, making the surface of the molten steel more easily oxidized and increasing the generation of inclusions. Therefore, the inclusion adsorption efficiency decreased significantly.

[0104] In summary, by pre-sintering alumina and titanium dioxide as the Al-Ti inhibitor, a stable Al-Ti-O network structure was formed in the melt, effectively reducing the reaction activity between the molten slag and the highly active Al-Ti molten steel. Alumina short fibers were introduced to form a reinforcing network, and nano silicon carbide and boron carbide were used to form a synergistic strengthening effect. A double bonding system was constructed using ethyl silicate hydrolysis solution, water glass, and sodium carboxymethyl cellulose to prepare a hollow-structured mold flux, effectively improving the mechanical strength of the mold flux and preventing the generation of overly fine particles during transportation and use from affecting the performance of the mold flux.

[0105] The above shows and describes 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 by the above embodiments. The above embodiments and descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles, characterized in that: The mold powder includes water-quenched melt particles, a composite binder, and ethyl silicate hydrolysis solution; Among them, the water-quenched melt particles include an Al-Ti inhibitor, a melt, alumina short fibers, and carbon black.

2. Preparation process of low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles, which is used to prepare the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles described in claim 1, and is characterized in that: It includes the following steps: Mix alumina and titanium dioxide and then press them into compacts. The molding pressure is 50 - 150 MPa, and the pressure holding time is 1 - 3 min. Then pre-sinter at 1300 - 1400 °C for 2 - 4 h and ball mill to obtain the Al-Ti inhibitor; Add calcium oxide, silicon dioxide, alumina, magnesia, zirconium dioxide, sodium oxide, calcium fluoride, and lithium carbonate to an electric arc furnace, heat up to 1550 - 1600 °C, introduce argon with a flow rate of 1 - 2 L / min, stir at 200 - 300 rpm and melt for 30 - 40 min, cool down to 1400 - 1450 °C, add the Al-Ti inhibitor, nano silicon carbide, and boron carbide, and keep warm for 20 - 30 min to obtain the melt; Inject the melt into a high-pressure water atomization system at a flow rate of 0.3 - 0.5 kg / min, and simultaneously add alumina short fibers and carbon black to form water-quenched melt particles; Mix the water-quenched melt particles, the composite binder, and the ethyl silicate hydrolysis solution to obtain a slurry, and dry the slurry with a centrifugal spray dryer to obtain hollow particles; After keeping the hollow particles at 400 - 500 °C for 20 - 30 min, heat them up to 800 - 850 °C at a rate of 10 °C / min in a tunnel furnace and keep warm for 8 - 10 min to obtain a low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles.

3. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 2, characterized in that: The mass ratio of the alumina to the titanium dioxide is 6 - 7:3.

5.

4. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 2, characterized in that: The particle size range of the Al-Ti inhibitor is 5 - 10 μm.

5. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 2, characterized in that: The calcium oxide is 23.7 - 29.5 parts by weight, the silicon dioxide is 23.5 - 29.2 parts by weight, the alumina is 11.8 - 14.7 parts by weight, the magnesia is 3.4 - 5.2 parts by weight, the zirconium dioxide is 2.2 - 4.8 parts by weight, the sodium oxide is 1.2 - 1.5 parts by weight, the calcium fluoride is 3.3 - 5.6 parts by weight, the lithium carbonate is 1.6 - 2 parts by weight, the Al-Ti inhibitor is 4.5 - 8.3 parts by weight, the nano silicon carbide is 0.4 - 0.9 parts by weight, the boron carbide is 0.3 - 0.6 parts by weight, the alumina short fibers are 1.7 - 3.5 parts by weight, the carbon black is 1.5 - 2.1 parts by weight, the composite binder is 6.2 - 8.4 parts by weight, and the ethyl silicate hydrolysis solution is 10.6 - 12.8 parts by weight.

6. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 2, characterized in that: The pressure of the high-pressure water atomization system is 8 - 10 MPa, and the water temperature is 18 - 22 °C.

7. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 2, characterized in that: The ethyl silicate hydrolysis solution is obtained from ethyl silicate, ethanol, and water in a mass ratio of 0.9 - 1.1:3 - 4:1, and the pH is 3 - 4.

8. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 2, characterized in that: The composite binder is obtained from water glass and sodium carboxymethyl cellulose in a mass ratio of 3:1, and the degree of substitution of sodium carboxymethyl cellulose is 0.6 - 0.

8.

9. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 7, characterized in that: The inlet temperature of the centrifugal spray dryer for drying is 250 - 255 °C, and the outlet temperature is 90 - 95 °C.

10. The preparation process of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles according to claim 7, characterized in that: The particle size range of the low-reactivity Al-Ti inhibition type mold powder for continuous casting based on pre-melted hollow particles is 0.6 - 0.8 mm.

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