Steelmaking continuous casting baking-free light long nozzle body material

Abstract

The invention discloses a steelmaking continuous casting baking-free light long nozzle body material, a long nozzle body is a CA6-Al2O3-C material, and the material comprises the following raw materials in percentage by mass: 34-50% of calcium hexaluminate, 8-14% of alumina hollow spheres, 10-20% of mullite, 10-18% of crystalline flake graphite, 5-15% of electrode graphite and nanocarbon, 2-4% of silicon carbide and 1-3% of metallic silicon. And 13-16% of resin is added to the binding agent. The raw material of the material also comprises 2-6% of nano aluminum oxide. According to the long nozzle body material, the whole long nozzle is light in weight, construction and installation are convenient, and the load bearing of equipment is reduced; the long nozzle body material is excellent in thermal shock resistance, the strength and thermal shock resistance of the material are improved, the anti-scouring and anti-erosion performance of the lightweight long nozzle is guaranteed, and preheating-free use is achieved. The lightweight long nozzle material is excellent in comprehensive performance and long in service life. Therefore, the requirements of light weight, no preheating and long service life of the long nozzle are comprehensively met, and continuous casting production of a steel mill and efficient and smooth operation of equipment are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking and continuous casting, in particular to a baking-free lightweight long shroud body material for steelmaking and continuous casting. Background Art

[0002] The shroud is an important functional refractory material in the continuous casting system. It is installed below the ladle outlet and is a sealed channel for molten steel to be injected from the ladle into the tundish. It plays a role in guiding the flow and preventing the oxidation and splashing of the molten steel. In order to achieve continuous casting protective pouring and immersion pouring and improve the quality of molten steel, the shroud installed on the 300-ton ladle of a certain enterprise is designed with a large trumpet-shaped caliber and a larger volume than the conventional cylindrical shroud. The volume density of the Al2O3-SiO2-C shroud body material in the existing technology is ≥2.45g / cm 3 , the finished shroud reaches 104kg / piece, which is inconvenient to construct and install, and the load-bearing equipment is overloaded. It cannot meet the promotion and application of existing equipment in various production lines of steel plants, and there is an urgent need for lightweight shrouds. When pouring steel, the temperature of the molten steel is above 1600℃. The huge temperature difference after pouring causes strong thermal stress in the shroud, which can easily lead to shroud breakage. If the shroud needs to be preheated to above 1000℃ before use, it will not only waste energy and aggravate C emissions, but also cause oxidation damage to the carbon-containing shroud during the baking preheating process, which affects its service life. Therefore, steel mills need a shroud that does not require preheating. In order to meet the all-round needs of steel mills, it is necessary to develop a lightweight, high-life, preheat-free continuous casting shroud.

[0003] The continuous casting nozzle usually consists of three parts: the body 1, the lining 2 and the slag line 3. Figure 1 The lining 2 of the shroud is usually very thin, about 3 to 5 mm, and the slag line 3 is relatively short, accounting for a small proportion of the volume of the shroud. Therefore, the weight of the shroud is basically determined by the weight of the body 1 material.

[0004] Chinese patent CN101205140A high carbon refractory material and its preparation method discloses the composition of the long nozzle (Al2O3-SiO2-C) material: 40-50% flake graphite, 8-15% silicon carbide and metallic silicon, 5-10% fused quartz, 7-12% fused zirconium mullite, 30-40% white corundum, 8-12% binder and resin. It is introduced that it has good resistance to erosion and scouring of molten steel and improves the operation rate of continuous casting.

[0005] Chinese patent CN15301195A no-bake carbon-free long nozzle discloses a special no-bake long nozzle Al2O3-SiO2-C (corundum-quartz-carbon) body material: flake graphite 20-40%, silicon carbide 4-8%, metallic silicon 0.5-4%, fused quartz 8-21%, fused zirconium mullite 8-18%, white corundum 30-56%, binder and resin 9%. The lining material is Al2O3-SiO2, and it is disclosed that the nozzle has good thermal shock resistance, erosion resistance and scour resistance.

[0006] Chinese patent CN1485295A aluminum-carbon continuous casting refractory material and its preparation method discloses an Al2O3-C long nozzle material, which uses white corundum, graphite, zirconium mullite, and silicon carbide as main raw materials, and also contains 0.5-5.0% boron nitride and 1.0-5.0% silicon carbide, and has good thermal shock stability and erosion resistance.

[0007] The main body of the existing shroud is made of Al2O3-SiO2-C or Al2O3-C materials, usually using corundum, fused quartz, zirconium mullite and graphite as the main raw materials to prepare the shroud. Fused corundum has a large grain structure, good corrosion resistance and thermal shock resistance, which can bring good performance to the baking-free shroud. However, the volume density of corundum is particularly high, reaching 3.95g / cm 3 Therefore, the weight of the refractory made of it is large, resulting in the bulk density of the long nozzle body made of corundum as the main raw material being basically 2.40-2.55g / cm 3 The bulk density of zirconium mullite raw materials is also very large, reaching 3.85-3.90 g / cm 3 , and the refractory materials made of it are also heavy.

[0008] The shroud is made of fused quartz because it has a low thermal expansion coefficient and excellent thermal shock resistance, which is beneficial to the shroud without preheating. However, fused quartz is rich in SiO2, which has poor corrosion resistance in molten steel and slag, and is not good for the life of the shroud. If the shroud material contains a large amount of SiO2, the following reactions will occur during the steel pouring process:

[0009] 2Mn + SiO2 = 2MnO + Si (1)

[0010] MnO + SiO2 = MnO·SiO2 (2)

[0011] SiO2 (s) + C(s) = SiO(g) + CO(g) (3)

[0012] This results in a decrease in the scouring and corrosion resistance of the nozzle material, which can easily cause production accidents. Therefore, in order to ensure the stability of the steel casting process and a long service life, it is necessary not only to achieve lightweighting of the nozzle, but also to minimize the SiO2 content in the nozzle material and increase the Al2O3 content to ensure a longer service life.

[0013] In order to ensure the life and application safety of the shroud during use, the development of a lightweight shroud must ensure good thermal shock resistance, corrosion resistance, and high-temperature strength performance, and find suitable lightweight raw materials for scientific combination to meet the steel plant's multi-dimensional needs of high life, no preheating, and lightweight. Summary of the invention

[0014] The purpose of the present invention is to provide a lightweight shroud body material for steelmaking continuous casting that does not require baking. The shroud body material makes the entire shroud lightweight, facilitates construction and installation, and reduces the load-bearing capacity of the equipment. The shroud body material has excellent thermal shock resistance and can be preheated-free. It has good resistance to erosion by molten steel and has a long service life.

[0015] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0016] A steelmaking continuous casting baking-free lightweight shroud body material, wherein the shroud body 1, an inner lining 2 and a slag line 3 form a continuous casting shroud, the shroud body is a CA6-Al2O3-C material, and the raw materials are calculated by mass percentage as follows: 34-50% calcium hexaaluminate, 8-14% hollow alumina balls, 10-20% mullite, 10-18% flake graphite, 5-15% electrode graphite and nano-carbon, 2-4% silicon carbide, 1-3% metallic silicon; and 13-16% binder and resin.

[0017] The raw material also includes nano aluminum oxide, with the nano aluminum oxide content being 2-6%.

[0018] The calcium hexaaluminate is a high-purity microporous calcium hexaaluminate lightweight raw material SLA-92.

[0019] The hollow alumina sphere is a closed and sealed sphere made by melting and blowing industrial alumina in an electric furnace, and the crystal form is a-Al2O3 microcrystal.

[0020] The Al2O3 content of the alumina hollow sphere is ≥99.0%, and the volume density is 1.1-1.5 g / cm 3 .

[0021] The ratio of the electrode graphite to the nanocarbon is 4:1.

[0022] The lining is made of Al2O3-SiO2 material, and the slag line is made of ZrO2-C material.

[0023] The steelmaking continuous casting baking-free lightweight shroud body material of the present invention is a CA6-Al2O3-C body material. By adding lightweight materials such as calcium hexaaluminate, hollow alumina balls, mullite, and a composite carbon source, and by adopting a composite nanotechnology of nano-carbon and nano-alumina for reinforcement, the thermal shock resistance, corrosion resistance and lightweight of the shroud material are achieved, fully meeting the functions of lightweight shroud, no preheating and long service life.

[0024] The present invention introduces calcium hexaaluminate as the main raw material. Calcium hexaaluminate (CA6) is the calcium aluminate phase with the highest Al2O3 content in the CaO-Al2O3 system, with a melting point higher than 1875°C and a thermal expansion coefficient of 8.0×10 -6 ℃ -1 It is a new type of refractory raw material that combines low expansion coefficient and high melting point. It has low solubility in steel slag; high stability in reducing atmosphere (CO); good chemical stability in alkaline environment; and low wettability to molten metal and slag (steel and non-ferrous metals). Calcium hexaaluminate itself has excellent high-temperature volume stability, thermal shock resistance and corrosion resistance. Specifically, the present invention selects high-purity microporous calcium hexaaluminate lightweight raw material SLA-92, whose volume density is 0.8g / cm 3 , is an average value, which is only 20% of the volume density of corundum, and can effectively reduce the weight of the entire long nozzle.

[0025] In order to further reduce the weight of the long nozzle, the present invention adopts some hollow alumina balls. The hollow alumina balls are closed and sealed balls made by melting and blowing industrial alumina in an electric furnace. The crystal form is a-Al2O3 microcrystals and the use temperature reaches 1800℃. The Al2O3 content of the raw material is ≥99.0%, the corrosion resistance is good, and the volume density is 1.1-1.5g / cm 3 , which is only 1 / 3 of the volume density of white corundum raw materials. The refractory materials made of it are light in weight, high in strength and good in corrosion resistance.

[0026] In order to further reduce the weight of the shroud, the present invention uses mullite, the bulk density of which is 2.75 g / cm 3 , which is 70% of the volume density of zirconium mullite, a conventional raw material for nozzles. Mullite has excellent thermal shock resistance and can replace fused quartz and zirconium mullite in existing conventional technologies, making the nozzle lighter and reducing SiO2 content, while maintaining good corrosion resistance and meeting the requirements for baking-free performance.

[0027] In order to enhance the strength, corrosion resistance and scouring resistance of the material of the present invention, the present invention uses nano-alumina as a reinforcing agent, and the nano-alumina is nano-alumina powder. The raw material has high activity and fast reaction. During use, it can promote the in-situ sintering of the nozzle material, greatly improve the density and high-temperature strength of the material, thereby improving the anti-scouring and anti-erosion performance of the material. The high strength also enhances the thermal shock resistance of the material, thereby ensuring the long life of the nozzle.

[0028] The present invention adopts composite carbon source technology, and the composite carbon source includes electrode graphite and nano-carbon. The workability and wettability of electrode graphite are better than those of conventional flake graphite, which can reduce the amount of binder added and improve the quality of nozzle materials. Nano-carbon is particularly fine and can improve the density and strength of the material. The composite carbon source technology greatly improves the corrosion resistance, density and strength of the product compared to the method of adding flake graphite alone. The amount of electrode graphite and nano-carbon added in the present invention is 5-15%, and the ratio is 4:1.

[0029] In order to ensure the stability of use, the steelmaking continuous casting baking-free light long nozzle is composed of three parts: body, lining and slag line. The light long nozzle body material of the present invention is CA6-Al2O3-C material, the lining material is carbon-free Al2O3-SiO2 material, and the slag line is ZrO2-C material.

[0030] Compared with the prior art, the present invention has the following beneficial effects: the shroud body material of the present invention makes the entire shroud lightweight, facilitates construction and installation, and reduces the load-bearing capacity of the equipment; the shroud body material has excellent thermal shock resistance, improves the strength and thermal shock resistance of the material, ensures the anti-scouring and anti-erosion performance of the lightweight shroud, and realizes preheating-free use. The lightweight shroud material has excellent comprehensive performance and a long service life. Therefore, the requirements of lightweight shroud, no preheating, and long service life are fully met, ensuring the efficient and smooth operation of continuous casting production and equipment in steel plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the long nozzle structure for continuous casting.

[0032] In the figure: 1 body, 2 lining, 3 slag line. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0034] When designing the baking-free lightweight shroud body material for steelmaking continuous casting, the present invention not only considers the thermal shock resistance and erosion resistance of the shroud body material, but also considers the lightweight of the shroud body material, thereby making the entire shroud lightweight, facilitating construction and installation, and reducing the load-bearing capacity of the equipment.

[0035] See also Figure 1A continuous casting long nozzle includes a body 1, a lining 2 and a slag line 3.

[0036] A steelmaking continuous casting baking-free lightweight shroud body material, the shroud body is a CA6-Al2O3-C material, and the raw materials are calculated by mass percentage: 34-50% calcium hexaaluminate, 8-14% hollow alumina balls, 10-20% mullite, 10-18% flake graphite, 5-15% electrode graphite and nano-carbon, 2-6% nano-alumina, 2-4% silicon carbide, 1-3% metallic silicon; and 13-16% binder and resin.

[0037] The calcium hexaaluminate (CA6) is a high-purity microporous calcium hexaaluminate lightweight raw material SLA-92, and its volume density is 0.8g / cm 3 .

[0038] The hollow alumina sphere is a closed and sealed sphere made by melting and blowing industrial alumina in an electric furnace, and the crystal form is a-Al2O3 microcrystal. The Al2O3 content in the hollow alumina sphere is ≥99.0%, and the volume density is 1.1-1.5g / cm 3 .

[0039] The raw material volume density of mullite is 2.75g / cm 3 .

[0040] The ratio of the electrode graphite to the nanocarbon is 4:1.

[0041] The lining is made of carbon-free Al2O3-SiO2 material, and the slag line is made of ZrO2-C material.

[0042] The steelmaking continuous casting baking-free lightweight shroud body material of the present invention is a CA6-Al2O3-C body material. By adding lightweight materials such as calcium hexaaluminate, hollow alumina balls, mullite, and a composite carbon source, and by adopting a composite nanotechnology of nano-carbon and nano-alumina for reinforcement, the thermal shock resistance, corrosion resistance and lightweight of the shroud material are achieved, fully meeting the functions of lightweight shroud, no preheating and long service life.

[0043] The lightweight shroud of the present invention is composed of three parts: the main body, the lining and the slag line. The CA6-Al2O3-C material of the shroud body is the main innovation of the present invention. The materials of the lining and the slag line remain unchanged, the lining material is a carbon-free Al2O3-SiO2 material, and the slag line is a ZrO2-C material. The production process of the shroud is the same as the conventional method.

[0044] Table 1 lists the proportions of the embodiments of the present invention and the comparative examples, and Table 2 shows the properties.

[0045] Table 1 Examples and Comparative Examples of Long Shroud Body Materials (wt%)

[0046]

[0047] When preparing the long nozzle, various solid raw materials except the binder liquid resin are mixed evenly, and then liquid phenolic resin is added to granulate and dry. Then the mixture is molded by isostatic pressing equipment at 150-170MPa. The molded product is fired at 1450-1550℃ in a reducing atmosphere, and then an anti-oxidation coating is applied on the surface of the product. After drying, it is the finished long nozzle.

[0048] Table 2 Performance of shroud body material embodiments and comparative examples

[0049]

[0050] As can be seen from Table 1 and Table 2, in Examples Q1 to Q4, due to the use of a variety of high-performance lightweight raw materials, the bulk density of the main material has been greatly reduced, and the weight of the nozzle has been reduced by about 12% compared with the original; although the present invention uses a variety of lightweight raw materials, the strength has not decreased, especially the high-temperature flexural strength is very high, indicating that the various raw materials are reasonably designed and properly combined, and the comprehensive performance at room temperature and high temperature is excellent. The long nozzle lightweight main body material of the present invention has achieved the predetermined goal. This embodiment achieves no baking, is installed on a 300-ton ladle, has excellent anti-erosion and scouring performance, and the service life reaches the user requirements of 8 to 10 furnaces of steel plants.

[0051] The present invention fully meets the requirements in terms of lightweight long shroud, no need for preheating, and long service life, thereby ensuring the efficient and smooth operation of continuous casting production and equipment in steel plants.

Claims

1. A steelmaking continuous casting baking-free lightweight shroud body material, wherein the shroud body (1), the lining (2) and the slag line (3) constitute the continuous casting shroud, and the characteristics are: The long nozzle body is made of CA6-Al2O3-C material, and the raw materials are calculated by mass percentage: 34-50% calcium hexaaluminate, 8-14% hollow alumina balls, 10-20% mullite, 10-18% flake graphite, 5-15% electrode graphite and nano-carbon, 2-4% silicon carbide, 1-3% metallic silicon; and 13-16% binder and resin.

2. According to claim 1, the steelmaking continuous casting baking-free lightweight long shroud body material is characterized by: The raw material also includes nano-alumina, with the nano-alumina content being 2-6%.

3. The steelmaking continuous casting baking-free lightweight shroud body material according to claim 1 or 2, characterized in that: The calcium hexaaluminate is a high-purity microporous calcium hexaaluminate lightweight raw material SLA-92.

4. The steelmaking continuous casting baking-free lightweight shroud body material according to claim 1 or 2, characterized in that: The hollow alumina sphere is a closed and sealed sphere made by melting and blowing industrial alumina in an electric furnace, and the crystal form is a-Al2O3 microcrystal.

5. The steelmaking continuous casting baking-free lightweight shroud body material according to claim 4 is characterized by: The Al2O3 content in the alumina hollow sphere is ≥99.0%, and the volume density is 1.1-1.5 g / cm 3 .

6. The steelmaking continuous casting baking-free lightweight shroud body material according to claim 1 or 2, characterized in that: The ratio of the electrode graphite to the nanocarbon is 4:

1.

7. The steelmaking continuous casting baking-free lightweight shroud body material according to claim 1 or 2, characterized in that: The lining is made of Al2O3-SiO2 material, and the slag line is made of ZrO2-C material.

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