Special casting powder for 904 super austenite

Abstract

The invention relates to the technical field of casting powder, in particular to special casting powder for 904 super austenite, which comprises calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, boric oxide, a SrO-CeO2-ZrO2 compound, an Al-C composition and sodium carboxymethyl cellulose. The SrO-CeO2-ZrO2 compound is prepared from cerous nitrate, zirconyl nitrate and strontium nitrate; according to the present invention, the SrO-CeO2-ZrO2 compound is adopted, the Al-C composition comprises aluminum powder and acetylene, the SrO-CeO2-ZrO2 compound and the Al-C composition are adopted, the unique oxygen vacancy characteristic of the SrO-CeO2-ZrO2 compound is utilized to enhance the Cr2O3 adsorption and decomposition ability, and the Al-C composition provides the reduction environment so as to effectively solve the slag layer failure problem caused by Cr2O3 active oxide inclusion in the continuous casting process of the high Cr, Ni and Mo alloy steel liquid.

Description

Technical Field

[0001] The present invention relates to the technical field of mold slag, in particular to a 904 super austenite special mold slag. Background Art

[0002] 904 super austenitic stainless steel is a high-alloy austenitic stainless steel with a low carbon content. It contains high levels of chromium, nickel, molybdenum and copper. The high chromium content enhances its resistance to oxidation and acidic corrosion. Nickel stabilizes the austenite structure and resists stress corrosion, and the high nickel content significantly reduces the sensitivity to stress corrosion cracking in chloride environments. Molybdenum is a core element for resisting pitting and crevice corrosion, giving super austenitic stainless steel high resistance to crevice corrosion and stress corrosion in chloride solutions. The addition of copper enhances its resistance to sulfuric acid corrosion. Therefore, super austenitic stainless steel not only has good machinability and weldability, and can be used in the manufacture of pressure vessels, etc., but also has excellent acid resistance, pitting corrosion resistance and crevice corrosion resistance, making it suitable for the manufacture of sulfuric acid reactors, submarine pipelines, flue gas desulfurization systems, etc.

[0003] However, due to the high content of active elements such as Cr, Ni, and Mo in 904 super austenitic stainless steel, inclusions such as Cr2O3 are oxidized at the molten steel-slag interface, which causes changes in the slag layer, affects the effect of the protective slag, and leads to defects on the surface of the ingot. In view of this, a special protective slag for 904 super austenitic stainless steel is provided. Summary of the Invention

[0004] The object of the present invention is to provide a special mold slag for 904 super austenite to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides a special mold flux for 904 super austenite, comprising a mold flux comprising calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, boron oxide, a SrO-CeO2-ZrO2 composite, an Al-C composition and sodium carboxymethyl cellulose;

[0006] The SrO-CeO2-ZrO2 composite was prepared from cerous nitrate, zirconyl nitrate and strontium nitrate;

[0007] The Al-C composition includes aluminum powder and acetylene.

[0008] As a further improvement of this technical solution, the specific preparation method of the SrO-CeO2-ZrO2 composite is as follows:

[0009] S1.1. Dissolve cerous nitrate, zirconyl nitrate, and strontium nitrate in deionized water and stir magnetically at 400-500 rpm for 30-40 minutes at 40-45°C.

[0010] S1.2. Adjust the pH to 9.5-10 by adding 1 mol / L ammonia water dropwise at a rate of 0.1-0.5 mL / min. Then, add 1-3 wt% sodium dodecylbenzenesulfonate and continue stirring for 1-2 h to form a precipitate.

[0011] S1.3. Separate the precipitate by centrifugation, wash with deionized water until neutral, dry at 40-50°C for 2-3 hours, calcine at 500-550°C for 3-4 hours, and ball-mill at 400-500 rpm for 4-5 hours to obtain a SrO-CeO2-ZrO2 composite.

[0012] An Al-C structure was prepared, and the C shell oxidized to generate CO gas, forming a local CO partial pressure, inhibiting the oxidation of Cr and Mo and delaying the premature oxidation reaction of Al. The Al core released active Al, which preferentially reduced FeO and Cr2O3 in the slag.

[0013] A SrO-CeO2-ZrO2 composite was prepared. This composite oxide has better thermal stability and oxidation resistance than CeO2. The redox effect of CeO2 is combined with the stable lattice of Zr to form a dynamic oxygen vacancy network. Zr in the composite induces lattice distortion, significantly increases the oxygen vacancy concentration, and inhibits the high-temperature growth of CeO2 grains. The composite structure prevents the phase change of CeO2 in a reducing atmosphere, improves the sintering resistance and phase stability, and exposes more active sites in the composite particles. Strontium can further inhibit the sintering of cerium and reduce its specific surface area decrease rate.

[0014] The Al-C composition works synergistically with the SrO-CeO2-ZrO2 complex, and SrO and Al2O3 can react to form a dense structure at the interface, preventing oxygen diffusion, thereby reducing the oxygen content in the steel, inhibiting the formation of inclusions, and improving the quality of 904 super austenitic stainless steel ingots.

[0015] As a further improvement of the present technical solution, the molar ratio of the cerous nitrate, zirconyl nitrate and strontium nitrate is 1-3:1:0.15-0.25.

[0016] As a further improvement of the present technical solution, the total metal ion concentration in the deionized water is 0.2-0.4 mol / L.

[0017] As a further improvement of the present technical solution, the specific preparation method of the Al-C composition is as follows:

[0018] S2.1. Ultrasonic cleaning of aluminum powder in 1-5% by mass dilute hydrochloric acid for 10 min to remove the surface oxide film, washing to neutrality, and drying at 60-65°C for 2 h to obtain activated aluminum nuclei;

[0019] S2.2. A carbon layer is vapor-deposited on the activated aluminum core at 500-550°C. The carbon source acetylene and the carrier gas argon are introduced at an acetylene flow rate of 50-60 mL / min and an argon flow rate of 200-210 mL / min. The deposition is performed for 1-1.5 hours. After deposition, the mixture is cooled to room temperature in argon to obtain an Al-C composite.

[0020] As a further improvement of the present technical solution, the acetylene / argon volume ratio is 1:4.

[0021] As a further improvement of the present technical solution, the thickness of the carbon layer is 1-2 μm.

[0022] As a further improvement of the present technical solution, the porosity of the carbon layer is 1-3%.

[0023] As a further improvement of the present technical solution, the calcium oxide is 32-35 parts by weight, the silicon dioxide is 27-31 parts by weight, the aluminum oxide is 11-16 parts by weight, the sodium oxide is 6-8 parts by weight, the calcium fluoride is 4-6 parts by weight, the boron oxide is 2-4 parts by weight, the SrO-CeO2-ZrO2 complex is 3-5 parts by weight, the Al-C composition is 6-9 parts by weight and the sodium carboxymethyl cellulose is 1-3 parts by weight.

[0024] As a further improvement of this technical solution, the specific preparation steps of the 904 super austenite special mold slag are as follows:

[0025] Calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride and boron oxide are mixed in proportion, melted to 1200°C under an inert atmosphere and kept warm for 1 hour, then quenched into glassy slag particles, ball-milled to 150-200 mesh powder, added with Al-C composition, mixed in a 0.1-0.2 MPa vacuum mixer for 20-30 minutes, and finally added with SrO-CeO2-ZrO2 composite. Ultrasonic dispersion is assisted by 40-45 kHz for 5-10 minutes to obtain a mixed powder. Sodium carboxymethyl cellulose is prepared into a solution with a mass fraction of 3-5%, and then sprayed into the mixed powder. Granulation is carried out using a twin-screw extruder under an inert atmosphere, and the particle size is controlled to be 0.5-1.0 mm. The powder is vacuum dried at 60-65°C for 12-24 hours to obtain a special protective slag for 904 super austenite.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The SrO-CeO2-ZrO2 composite is used in the special protective slag for 904 super austenite, which effectively solves the problem of slag layer failure caused by Cr2O3 active oxide inclusions during the continuous casting process of high Cr, Ni, and Mo alloy steel liquid. The SrO-CeO2-ZrO2 composite is prepared by a co-precipitation method. Its unique oxygen vacancy characteristics can enhance the adsorption and decomposition ability of Cr2O3. The Al-C composition works through a two-step reaction mechanism. On the one hand, aluminum powder reacts with FeO and Cr2O3 to reduce the formation of inclusions. On the other hand, the carbon layer synergistically forms a local reducing microenvironment, successfully eliminating defects such as cracks and depressions on the surface of the ingot, meeting the requirements of the protective slag for the high Cr, Ni, and Mo active elements of 904 super austenite and avoiding the generation of a large number of Cr2O3 inclusions. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] 904 super austenite special mold slag, the mold slag includes calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, boron oxide, SrO-CeO2-ZrO2 complex, Al-C composition and sodium carboxymethyl cellulose;

[0030] The SrO-CeO2-ZrO2 composite was prepared from cerous nitrate, zirconyl nitrate and strontium nitrate;

[0031] The Al-C composition includes aluminum powder and acetylene;

[0032] Example 1: In this example, the specific preparation method of the 904 super austenite special mold slag is as follows:

[0033] 35 parts by weight of calcium oxide, 31 parts by weight of silicon dioxide, 16 parts by weight of aluminum oxide, 8 parts by weight of sodium oxide, 6 parts by weight of calcium fluoride, 4 parts by weight of boron oxide, 3 parts by weight of SrO-CeO2-ZrO2 composite, 6 parts by weight of Al-C composition and 3 parts by weight of sodium carboxymethyl cellulose;

[0034] The SrO-CeO2-ZrO2 composite was prepared from cerous nitrate, zirconyl nitrate and strontium nitrate; the molar ratio of cerous nitrate, zirconyl nitrate and strontium nitrate was 3:1:0.15;

[0035] The Al-C composition includes aluminum powder and acetylene; the volume ratio of acetylene to argon is 1:4;

[0036] S1.1, cerous nitrate, zirconyl nitrate, strontium nitrate were dissolved in deionized water, the total metal ion concentration in deionized water was 0.2 mol / L, and the solution was stirred at 40℃ and 400 rpm for 30 min;

[0037] S1.2, 1 mol / L ammonia water was added dropwise at a speed of 0.5 mL / min to adjust the pH to 10, then 3 wt% sodium dodecyl benzene sulfonate was added, and the stirring was continued for 2 h to generate a precipitate;

[0038] S1.3, the precipitate was centrifuged and washed with deionized water until neutral, then dried at 50℃ for 3 h, calcined at 550℃ for 4 h, and ball milled at 500 rpm for 5 h to obtain a SrO-CeO2-ZrO2 composite;

[0039] S2.1, the aluminum powder was ultrasonically cleaned in 5% dilute hydrochloric acid for 10 min to remove the surface oxide film, washed to neutral, and dried at 60℃ for 2 h to obtain an active aluminum core;

[0040] S2.2, the active aluminum core was vapor deposited with a carbon layer at 500℃, and the carbon source was acetylene, and the carrier gas was argon, the flow rate of acetylene was 50 mL / min, and the flow rate of argon was 200 mL / min, the deposition was carried out for 1 h, and the deposition was cooled to room temperature in argon to obtain an Al-C composition;

[0041] Calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, boron oxide were mixed in proportion, melted to 1200℃ under inert atmosphere for 1 h, then water-quenched into glassy slag particles, ball milled into 200 mesh powder, mixed with the Al-C composition in a 0.1 MPa vacuum stirrer for 20 min, finally added with the SrO-CeO2-ZrO2 composite, ultrasonically dispersed for 5 min at 40 kHz, to obtain a mixed powder, a 3% by mass sodium carboxymethyl cellulose solution was prepared, then sprayed onto the mixed powder, granulated using a double screw extruder under inert atmosphere, the particle size was controlled at 0.5 mm, and vacuum dried at 60℃ for 12 h to obtain a 904 super austenite special protective slag.

[0042] In this embodiment, the specific preparation method of the 904 super austenite special protective slag is as follows:

[0043] Calcium oxide 35 parts by weight, silicon dioxide 31 parts by weight, aluminum oxide 16 parts by weight, sodium oxide 8 parts by weight, calcium fluoride 6 parts by weight, boron oxide 4 parts by weight, SrO-CeO2-ZrO2 composite 4 parts by weight, Al-C composition 7.5 parts by weight, and sodium carboxymethyl cellulose 3 parts by weight;

[0044] The SrO-CeO2-ZrO2 composite was prepared from cerous nitrate, zirconyl nitrate and strontium nitrate; the molar ratio of cerous nitrate, zirconyl nitrate and strontium nitrate was 3:1:0.15;

[0045] The Al-C composition includes aluminum powder and acetylene; the volume ratio of acetylene to argon is 1:4;

[0046] S1.1. Dissolve cerous nitrate, zirconium oxynitrate, and strontium nitrate in deionized water to a total metal ion concentration of 0.2 mol / L. Stir magnetically at 400 rpm for 30 min at 40°C.

[0047] S1.2. Adjust the pH to 10 by adding 1 mol / L ammonia water dropwise at a rate of 0.5 mL / min. Then, add 3 wt% sodium dodecylbenzenesulfonate and continue stirring for 2 h to form a precipitate.

[0048] S1.3. The precipitate was separated by centrifugation, washed with deionized water until neutral, dried at 50°C for 3 h, calcined at 550°C for 4 h, and ball-milled at 500 rpm for 5 h to obtain a SrO-CeO2-ZrO2 composite.

[0049] S2.1. Ultrasonic cleaning of aluminum powder in 5% by mass dilute hydrochloric acid for 10 min to remove the surface oxide film, washing to neutrality, and drying at 60°C for 2 h to obtain activated aluminum nuclei.

[0050] S2.2, vapor-depositing a carbon layer on the activated aluminum core at 500°C by introducing acetylene as a carbon source and argon as a carrier gas at a flow rate of 50 mL / min for acetylene and 200 mL / min for argon for 1 h. After deposition, the layer was cooled to room temperature in argon to obtain an Al-C composite.

[0051] Calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, and boron oxide are mixed in proportion, melted to 1200°C under an inert atmosphere and kept warm for 1 hour, then quenched into glassy slag particles, ball-milled to 200 mesh powder, added with Al-C composition, mixed in a 0.1 MPa vacuum mixer for 20 minutes, and finally added with SrO-CeO2-ZrO2 composite. 40kHz ultrasonic-assisted dispersion is used for 5 minutes to obtain a mixed powder. Sodium carboxymethyl cellulose is made into a solution with a mass fraction of 3%, and then sprayed into the mixed powder. Granulation is carried out using a twin-screw extruder under an inert atmosphere, and the particle size is controlled at 0.5 mm. The mixture is vacuum-dried at 60°C for 12 hours to obtain 904 super austenite special protective slag.

[0052] Example 3: In this example, the specific preparation method of the 904 super austenite special mold slag is as follows:

[0053] 35 parts by weight of calcium oxide, 31 parts by weight of silicon dioxide, 16 parts by weight of aluminum oxide, 8 parts by weight of sodium oxide, 6 parts by weight of calcium fluoride, 4 parts by weight of boron oxide, 5 parts by weight of SrO-CeO2-ZrO2 composite, 9 parts by weight of Al-C composition and 3 parts by weight of sodium carboxymethyl cellulose;

[0054] The SrO-CeO2-ZrO2 composite was prepared from cerous nitrate, zirconyl nitrate and strontium nitrate; the molar ratio of cerous nitrate, zirconyl nitrate and strontium nitrate was 3:1:0.15;

[0055] The Al-C composition includes aluminum powder and acetylene; the volume ratio of acetylene to argon is 1:4;

[0056] S1.1. Dissolve cerous nitrate, zirconium oxynitrate, and strontium nitrate in deionized water to a total metal ion concentration of 0.2 mol / L. Stir magnetically at 400 rpm for 30 min at 40°C.

[0057] S1.2. Adjust the pH to 10 by adding 1 mol / L ammonia water dropwise at a rate of 0.5 mL / min. Then, add 3 wt% sodium dodecylbenzenesulfonate and continue stirring for 2 h to form a precipitate.

[0058] S1.3. The precipitate was separated by centrifugation, washed with deionized water until neutral, dried at 50°C for 3 h, calcined at 550°C for 4 h, and ball-milled at 500 rpm for 5 h to obtain a SrO-CeO2-ZrO2 composite.

[0059] S2.1. Ultrasonic cleaning of aluminum powder in 5% by mass dilute hydrochloric acid for 10 min to remove the surface oxide film, washing to neutrality, and drying at 60°C for 2 h to obtain activated aluminum nuclei.

[0060] S2.2, vapor-depositing a carbon layer on the activated aluminum core at 500°C by introducing acetylene as a carbon source and argon as a carrier gas at a flow rate of 50 mL / min for acetylene and 200 mL / min for argon for 1 h. After deposition, the layer was cooled to room temperature in argon to obtain an Al-C composite.

[0061] Calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, and boron oxide are mixed in proportion, melted to 1200°C under an inert atmosphere and kept warm for 1 hour, then quenched into glassy slag particles, ball-milled to 200 mesh powder, added with Al-C composition, mixed in a 0.1 MPa vacuum mixer for 20 minutes, and finally added with SrO-CeO2-ZrO2 composite. 40kHz ultrasonic-assisted dispersion is used for 5 minutes to obtain a mixed powder. Sodium carboxymethyl cellulose is made into a solution with a mass fraction of 3%, and then sprayed into the mixed powder. Granulation is carried out using a twin-screw extruder under an inert atmosphere, and the particle size is controlled at 0.5 mm. The mixture is vacuum-dried at 60°C for 12 hours to obtain 904 super austenite special protective slag.

[0062] Example 4: In this example, the specific preparation method of the 904 super austenite special mold slag is as follows:

[0063] 45 parts by weight of calcium oxide, 30 parts by weight of silicon dioxide, 16 parts by weight of aluminum oxide, 8 parts by weight of sodium oxide, 6 parts by weight of calcium fluoride, 4 parts by weight of boron oxide, 5 parts by weight of SrO-CeO2-ZrO2 composite, 9 parts by weight of Al-C composition and 3 parts by weight of sodium carboxymethyl cellulose;

[0064] The SrO-CeO2-ZrO2 composite was prepared from cerous nitrate, zirconyl nitrate and strontium nitrate; the molar ratio of cerous nitrate, zirconyl nitrate and strontium nitrate was 3:1:0.15;

[0065] The Al-C composition includes aluminum powder and acetylene; the volume ratio of acetylene to argon is 1:4;

[0066] S1.1. Dissolve cerous nitrate, zirconium oxynitrate, and strontium nitrate in deionized water to a total metal ion concentration of 0.2 mol / L. Stir magnetically at 400 rpm for 30 min at 40°C.

[0067] S1.2. Adjust the pH to 10 by adding 1 mol / L ammonia water dropwise at a rate of 0.5 mL / min. Then, add 3 wt% sodium dodecylbenzenesulfonate and continue stirring for 2 h to form a precipitate.

[0068] S1.3. The precipitate was separated by centrifugation, washed with deionized water until neutral, dried at 50°C for 3 h, calcined at 550°C for 4 h, and ball-milled at 500 rpm for 5 h to obtain a SrO-CeO2-ZrO2 composite.

[0069] S2.1. Ultrasonic cleaning of aluminum powder in 5% by mass dilute hydrochloric acid for 10 min to remove the surface oxide film, washing to neutrality, and drying at 60°C for 2 h to obtain activated aluminum nuclei.

[0070] S2.2, vapor-depositing a carbon layer on the activated aluminum core at 500°C by introducing acetylene as a carbon source and argon as a carrier gas at a flow rate of 50 mL / min for acetylene and 200 mL / min for argon for 1 h. After deposition, the layer was cooled to room temperature in argon to obtain an Al-C composite.

[0071] Calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, boron oxide are mixed in proportion, melted to 1200 DEG C under inert atmosphere for 1h, then water quenching into glassy slag particles, ball milling to 200 mesh powder, adding Al-C composition, mixing in 0.1 MPa vacuum stirrer for 20 min, finally adding SrO-CeO2-ZrO2 compound, 40 kHz ultrasonic assisted dispersion for 5 min, to obtain mixed powder, then spraying sodium carboxymethyl cellulose solution with mass fraction of 3% into the mixed powder, using a twin-screw extruder to granulate under inert atmosphere, controlling the particle size at 0.5 mm, vacuum drying at 60 DEG C for 12h, to obtain the 904 super austenite special protective slag.

[0072] Comparative Example 1: using the method of Example 3, without adding SrO-CeO2-ZrO2 compound.

[0073] Comparative Example 2: using the method of Example 3, without adding Al-C composition.

[0074] Comparative Example 3: using the method of Example 3, directly physically mixing SrO, CeO2 and ZrO2 for addition.

[0075] Comparative Example 4: using the method of Example 3, directly physically mixing Al and C for addition.

[0076] The present application prepares 904 super austenite special protective slag, and the performance index test items and test standards of the 904 super austenite special protective slag are as follows:

[0077] Take the protective slag and molten steel sample containing non-metallic inclusions, in order to simulate the high temperature environment in the continuous casting process, put the molten steel sample into a 1300 DEG C high temperature furnace, uniformly add the protective slag into the molten steel sample, separate the protective slag and the molten steel, detect the types and quantities of inclusions, compare the content of inclusions in the molten steel before and after adsorption to calculate the removal rate (%); cut the sample with a length of ≥1m from the head, middle and tail of the continuous casting billet (avoid the cutting end face 50 cm), polish the scale with a grinding wheel, clean with alcohol and dry, ensure that the surface is not contaminated, under the light intensity ≥1000Lux shadowless lamp, visually inspect the surface at an angle of 30 DEG, visually screen the crack, pore, slag inclusion and other defect areas, determine the defect grade, the specific determination standard is as follows:

[0078] 0 level: smooth surface, no visible cracks, pits, slag inclusions or scale residues, which does not mean completely no defects;

[0079] 1 level: local slight scratch or pitting, defect length ≤10mm, depth ≤0.1mm, defect number per square meter ≤3;

[0080] Level 2: Crack length ≤ 20mm, width ≤ 0.2mm; pit diameter ≤ 2mm, depth ≤ 0.3mm, number of defects per square meter ≤ 5;

[0081] Level 3: Crack length ≤ 50mm, width ≤ 0.5mm; pit diameter ≤ 5mm, depth ≤ 0.5mm, number of defects per square meter ≤ 10;

[0082] Level 4: Crack length ≥50mm, width ≥0.5mm; pit diameter ≥5mm, depth ≥0.5mm, number of defects per square meter ≤15;

[0083] Level 5 (Unqualified): Large cracks (length ≥ 100 mm), deep pits (depth ≥ 1 mm) or slag inclusions, with dense distribution of defects (number ≥ 20 / m²).

[0084] The 904 super austenite special mold slag prepared in Examples 1-4 and Comparative Examples 1-4 was tested according to the above standards, and the obtained data are shown in Table 1:

[0085] Table 1 Performance data of Examples 1-4 and Comparative Examples 1-4

[0086] By comparing Examples 1-4 with Comparative Examples 1-4, it can be seen that in the 904 super austenite special mold flux, the SrO-CeO2-ZrO2 complex has a significant impact on the mold flux.

[0087] According to Examples 1-3, it can be seen that with the increasing weight of the SrO-CeO2-ZrO2 composite and the Al-C composition, the effect of removing inclusions in the 904 super austenite special mold slag is better. This is because Zr induces CeO2 lattice distortion, forms a dynamic oxygen vacancy network, preferentially adsorbs and consumes oxygen atoms at the steel liquid interface, inhibits Cr oxidation to generate Cr2O3, and SrO inhibits the high-temperature growth of CeO2 grains, inhibits the sintering of cerium, reduces its specific surface area reduction rate, provides more active sites, and thus enhances The deoxidizing property of cerium and the carbon layer in the Al-C composition delay the oxidation of the Al nucleus, release active Al at high temperature, and preferentially reduce Cr2O3 in the slag. A synergistic effect is formed between the SrO-CeO2-ZrO2 complex and the Al-C composition, forming a dense barrier to reduce the oxygen diffusion coefficient and block the secondary oxidation path of the molten steel. Therefore, the synergistic effect of the SrO-CeO2-ZrO2 complex and Al-CaO-C significantly improves the inclusion removal rate and reduces the defect level by inhibiting oxidation and providing reduction.

[0088] According to Examples 3 and 4, as the ratio of calcium oxide to silicon dioxide changes, that is, the alkalinity of the protective slag changes, the effect of removing inclusions in the 904 super austenite special protective slag decreases. This is because high alkalinity will cause the silicate structure to transform from chain to island, the slag viscosity will increase significantly, and the fluidity will decrease, which will lead to the obstruction of the floating of inclusions and weaken the inclusion removal ability.

[0089] According to the above test experiments, Example 3 is adopted as the optimal example and compared with Comparative Examples 1-4 respectively.

[0090] By comparing Example 3 with Comparative Example 1, it can be seen that when the SrO-CeO2-ZrO2 complex is not added, the effect of removing inclusions in the 904 super austenite special protective slag is worse. This is because the oxygen vacancy network of the SrO-CeO2-ZrO2 complex is missing, and oxygen atoms at the steel liquid interface freely diffuse to the slag layer, the Cr oxidation reaction is aggravated, and there is no dense barrier protection. The pores in the slag layer are not filled, and the oxygen diffusion channels are open, which directly leads to runaway oxidation and a surge in defects. The effect of removing inclusions in the 904 super austenite special protective slag is poor.

[0091] By comparing Example 3 with Comparative Example 2, it can be seen that without adding the Al-C composition, the effect of removing inclusions in the 904 super austenite special protective slag is worse. This is because without adding the Al-C composition, there is a lack of active reducing agent, and the protective slag only relies on passive adsorption of the basic components, resulting in continuous generation of Cr2O3, and the aggregation of inclusions leads to increased viscosity of the slag layer, decreased fluidity, and obstruction of the floating of inclusions. Therefore, the effect of removing inclusions in the 904 super austenite special protective slag is poor.

[0092] By comparing Example 3 with Comparative Example 3, it can be seen that the more SrO, CeO2 and ZrO2 are physically mixed and added directly, the worse the effect of removing inclusions in the 904 super austenite special protective slag. This is because physical mixing cannot form a ZrO2 and CeO2 complex, the oxygen vacancy concentration is low, and the grain size of the uncompounded CeO2 particles increases at high temperatures, the specific surface area decreases, the active sites decrease, and the efficiency of the component action is low, resulting in poor inclusion removal effect in the 904 super austenite special protective slag.

[0093] By comparing Example 3 and Comparative Example 4, it can be seen that the more Al and C are physically mixed and added, the worse the effect of removing inclusions in the 904 super austenite special protective slag. This is because Al is directly exposed to the slag without passing through the coating structure of the carbon layer and reacts instantly to form Al2O3. The instantaneous generation of a large amount of Al2O3 will cause the pores of the slag layer to be blocked, which in turn hinders the adsorption of inclusions. Therefore, the effect of removing inclusions in the 904 super austenite special protective slag is poor.

[0094] In summary, by preparing the SrO, CeO2, ZrO2 composite, the interface oxygen ions are adsorbed by the redox effect of CeO2 to inhibit the generation of Cr2O3 inclusions, SrO inhibits the high-temperature growth of CeO2 grains, high specific surface area enhances activity, C shell oxidation generates CO gas to inhibit Cr oxidation, and Al release is delayed, active Al is released in stages at high temperature, Cr2O3 in the slag is preferentially reduced, SrO and Al2O3 react to form a dense barrier, further blocking the oxygen diffusion channel, and reducing the oxygen permeability. Therefore, the SrO-CeO2-ZrO2 composite inhibits oxygen permeation, Al-C provides a reducing environment, and cooperates to double-block the oxidation path, effectively improving the effect of the protective slag on removing inclusions.

[0095] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. 904 super austenite special mold slag, characterized by: The mold slag includes calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, boron oxide, SrO-CeO2-ZrO2 composite, Al-C composite and sodium carboxymethyl cellulose; The SrO-CeO2-ZrO2 composite was prepared from cerous nitrate, zirconyl nitrate and strontium nitrate; The Al-C composition includes aluminum powder and acetylene.

2. The 904 super austenite special mold slag according to claim 1, characterized in that: The specific preparation method of the SrO-CeO2-ZrO2 composite is as follows: S1.

1. Dissolve cerous nitrate, zirconyl nitrate, and strontium nitrate in deionized water and stir magnetically at 400-500 rpm for 30-40 min at 40-45°C. S1.

2. Adjust the pH to 9.5-10 by adding 1 mol / L ammonia water dropwise at a rate of 0.1-0.5 mL / min. Then, add 1-3 wt% sodium dodecylbenzenesulfonate and continue stirring for 1-2 h to form a precipitate. S1.

3. Separate the precipitate by centrifugation, wash with deionized water until neutral, dry at 40-50°C for 2-3 hours, calcine at 500-550°C for 3-4 hours, and ball-mill at 400-500 rpm for 4-5 hours to obtain a SrO-CeO2-ZrO2 composite.

3. The 904 super austenite special mold slag according to claim 2, characterized in that: The molar ratio of the cerous nitrate, zirconyl nitrate and strontium nitrate is 1-3:1:0.15-0.

25.

4. The 904 super austenite special mold slag according to claim 2, characterized in that: The total metal ion concentration in the deionized water is 0.2-0.4 mol / L.

5. The 904 super austenite special mold slag according to claim 1, characterized in that: The specific preparation method of the Al-C composition is as follows: S2.

1. Ultrasonic cleaning of aluminum powder in 1-5% by mass dilute hydrochloric acid for 10 min to remove the surface oxide film, washing to neutrality, and drying at 60-65°C for 2 h to obtain activated aluminum nuclei; S2.

2. A carbon layer is vapor-deposited on the activated aluminum core at 500-550°C. The carbon source acetylene and the carrier gas argon are introduced at an acetylene flow rate of 50-60 mL / min and an argon flow rate of 200-210 mL / min. The deposition is performed for 1-1.5 hours. After deposition, the mixture is cooled to room temperature in argon to obtain an Al-C composite.

6. The 904 super austenite special mold slag according to claim 5, characterized in that: The acetylene / argon volume ratio=1:

4.

7. The 904 super austenite special mold slag according to claim 5, characterized in that: The carbon layer has a thickness of 1-2 μm.

8. The 904 super austenite special mold slag according to claim 5, characterized in that: The porosity of the carbon layer is 1-3%.

9. The 904 super austenite special mold slag according to claim 1, characterized in that: The calcium oxide is 32-35 parts by weight, the silicon dioxide is 27-31 parts by weight, the aluminum oxide is 11-16 parts by weight, the sodium oxide is 6-8 parts by weight, the calcium fluoride is 4-6 parts by weight, the boron oxide is 2-4 parts by weight, the SrO-CeO2-ZrO2 complex is 3-5 parts by weight, the Al-C composition is 6-9 parts by weight and the sodium carboxymethyl cellulose is 1-3 parts by weight.

10. The 904 super austenite special mold slag according to claim 1, characterized in that: The specific preparation steps of the 904 super austenite special mold slag are: Calcium oxide, silicon dioxide, aluminum oxide, sodium oxide, calcium fluoride, and boron oxide are mixed in proportion, melted to 1200°C under an inert atmosphere and kept warm for 1 hour, then quenched into glassy slag particles, ball-milled to 150-200 mesh powder, added with Al-C composition, mixed in a 0.1-0.2 MPa vacuum mixer for 20-30 minutes, and finally added with SrO-CeO2-ZrO2 composite. 40-45kHz ultrasonic-assisted dispersion is performed for 5-10 minutes to obtain a mixed powder. Sodium carboxymethyl cellulose is prepared into a solution with a mass fraction of 3-5%, and then sprayed into the mixed powder. Granulation is carried out using a twin-screw extruder under an inert atmosphere, and the particle size is controlled to be 0.5-1.0 mm. The powder is vacuum dried at 60-65°C for 12-24 hours to obtain a special protective slag for 904 super austenite.

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