Air brick protecting material, preparation method and application thereof

Abstract

This invention provides a protective material for permeable bricks, its preparation method, and its application, belonging to the field of metallurgical auxiliary materials technology. The protective material for permeable bricks is made from the following raw materials: 10-30 parts by weight of magnesium aluminum spinel, 30-60 parts by weight of electrofused refining slag, 5-20 parts by weight of magnesia, 5-15 parts by weight of white corundum, and 10-20 parts by weight of fluorite. The protective material for permeable bricks provided by this invention is used to improve the air permeability and service life of permeable bricks.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical auxiliary materials technology, specifically relating to a permeable brick protective material, its preparation method and its application. Background Technology

[0002] With increasingly stringent requirements for steel quality, improvements to steelmaking technology and processes are necessary. Ladle refining is a crucial refining process in steelmaking, allowing for the regulation of steel composition and molten steel temperature. Permeable bricks are the most critical functional component for the successful implementation of this process, playing a vital role in the reliability and completeness of ladle refining.

[0003] The use of permeable bricks is discontinuous; they need to be replaced every time a ladle comes off the production line. Different physical and chemical corrosion occurs at different times throughout the ladle's lifespan. Field experience shows that the main causes of permeable brick damage include molten steel erosion, thermal stress, mechanical stress, oxygen blowing, and slag erosion. During normal operation, cold steel easily accumulates on the working surface of the permeable bricks. Because the viscosity of this accumulated cold steel is relatively high, it hinders air blowing. Therefore, to meet refining requirements, the blowing pressure needs to be increased, which further leads to structural spalling. Severe penetration can block the air passages, reducing the blowing efficiency and service life. Therefore, developing a protective material specifically for permeable bricks is essential. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a protective material for breathable bricks, which improves the air permeability and service life of breathable bricks, in order to address the shortcomings of the prior art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A breathable brick protective material is made from the following raw materials: 10-30 parts by weight of magnesium aluminum spinel, 30-60 parts by weight of electrofused refining slag, 5-20 parts by weight of magnesia, 5-15 parts by weight of white corundum, and 10-20 parts by weight of fluorite.

[0007] Preferably, the particle size of the magnesium aluminum spinel, fused refining slag, magnesia, white corundum and fluorite is 0.3-1.0 mm.

[0008] As a preferred option, the selected magnesium aluminum spinel composition is: MgO: 25.0-31.0%, Al2O3: 69.0-75.0%;

[0009] Composition of fused refining slag: SiO2 ≤ 3.0%, CaO: 47.0-53.0%, Al2O3: 37.0-43.0%;

[0010] Magnesia composition: MgO ≥ 97.0%;

[0011] White fused alumina composition: Al2O3 ≥ 99.0%;

[0012] Fluorite composition: SiO2≤6.0%, CaF2≥90.0%.

[0013] Preferably, the effective component composition of the above-mentioned permeable brick protective material, by mass percentage, is: SiO2 ≤ 3.0%, CaO 15.45-30.75%, MgO 8.5-28.5%, Al2O3 27.5-37.5%, CaF 29.05-18.50%, H2O ≤ 0.50%, with the balance being loss on ignition and impurities. The impurities may be Fe2O3 or TiO2, but are not limited to these, and the content of each impurity is less than 1%.

[0014] As a preferred embodiment, the preparation method of the above-mentioned permeable brick protective material includes: providing 10-30 parts by weight of magnesium aluminum spinel, 30-60 parts by weight of fused refining slag, 5-20 parts by weight of magnesia, 5-15 parts by weight of white corundum, and 10-20 parts by weight of fluorite, wherein the particle size of the magnesium aluminum spinel, fused refining slag, magnesia, white corundum, and fluorite is 0.3-1.0 mm; screening and dust removal of each raw material; stirring and mixing evenly; testing; and packaging and warehousing.

[0015] As a preferred option, the above-mentioned permeable brick protective material is applied to the refining of aluminum-containing, titanium-containing, or ultra-low carbon steel ladles. Specifically, before the aluminum-containing, titanium-containing, or ultra-low carbon steel is tapped, it is evenly added to the upper surface of the permeable brick through a pipe to completely cover it.

[0016] The function of the permeable brick is essentially to act as a channel for argon gas to be blown into molten steel. Its basic working principle is as follows: argon gas enters the molten steel through the narrow slits in the permeable brick core, disperses as bubbles, and rises. Driven by buoyancy, the surrounding molten steel forms an upward flow above the permeable brick. Reaching the top of the molten steel, it turns horizontally and then flows downwards along the ladle wall, causing the molten steel to circulate within the ladle. This facilitates the rapid melting of alloys and fluxes added to the molten steel, promotes uniformity of steel composition and temperature, and allows inclusions in the molten steel to float to the surface. It also removes non-metallic inclusions and harmful gases from the steel, achieving the purpose of refining the molten steel.

[0017] like Figure 1As shown, the bottom-blown permeable bricks in a ladle must withstand the scouring of molten steel, thermal stress, mechanical stress, oxygen blowing, and slag erosion during the production process. Specifically, 1) Scouring of molten steel: During the refining process, molten steel is stirred by argon throughout. High-speed, high-pressure airflow is blown into the ladle through the permeable bricks, giving the molten steel a certain stirring kinetic energy. The stirring intensity of the molten steel is controlled by controlling the gas flow rate. The phenomenon that people can see is that the molten steel in the ladle boils. At this time, the gas at the bottom of the ladle interacts with the molten steel to form turbulence. At the same time, due to the backflow of the airflow, the permeable bricks and the surrounding refractory materials are severely scouring. 2) Thermal Stress: The baking temperature of the ladle is around 1000℃. During the converter tapping process, the working layer of the permeable brick comes into contact with molten steel at temperatures above 1600℃, generating significant thermal stress. Furthermore, the thermal stress varies depending on the location of the permeable brick due to temperature changes. Simultaneously, high-pressure, high-speed, and low-temperature airflow continuously blows out from the narrow slits of the permeable brick. During one working cycle of the permeable brick, the temperature changes frequently, resulting in a temperature gradient within the permeable brick. When the thermal stress around the working layer of the permeable brick exceeds its own bonding strength, cracks will appear under thermal shock, causing the permeable brick layer to fracture. 3) Mechanical Stress: The permeable brick itself is a multi-phase composite material. Due to its structural characteristics, it has many defects and cracks. In addition, the material is designed for enhanced corrosion resistance, making it easy to initiate cracks in the permeable brick itself. During use, the working layer of the permeable brick repeatedly comes into contact with high-temperature molten steel, and the refractory material at the bottom of the ladle experiences temperature differences due to continuous high and low temperature changes. Due to the difference in the expansion coefficients between the original and modified layers of the refractory material, the permeable bricks are subjected to shear stress, leading to the initiation and propagation of existing cracks, and in severe cases, transverse cracks or even breakage. 4) Oxygen blowing: In the later stages of use, the surface of the working layer of the permeable bricks will be lower than that of the base bricks. Under normal circumstances, residual steel and slag are easily retained in the working layer, and the viscosity is relatively high, which hinders normal argon blowing. To ensure the permeability of the permeable bricks, during hot ladle repair, the residual steel and slag remaining on the working layer of the permeable bricks must be blown away with an oxygen blowing pipe and melted. If the distance between the oxygen blowing pipe and the surface of the permeable bricks is not appropriate, it is easy to cause the brick core to burn unevenly, forming a slope, which accelerates the damage of the permeable bricks. 5) Slag erosion: After the steel ladle is poured, the slag remaining in the ladle needs to be recycled again. The slag usually needs to wait in the ladle for 10 to 15 minutes. During this time, the working surface of the permeable brick is in full contact with the slag. The slag continuously penetrates into the brick along the working surface of the permeable brick. The oxides such as CaO, FeO, MnO, SiO2, and Fe2O3 in the slag react with the permeable brick to generate low-melting-point substances. These substances are easily eroded by scouring.

[0018] Therefore, it is evident that the burn-off of permeable bricks is caused by a variety of factors. The combined effect of these complex factors results in a very limited lifespan for permeable bricks, necessitating frequent replacements. This disrupts ladle turnover and production rhythm, increases the cost of refractory materials per ton of steel, and negatively impacts the current trend towards larger ladle sizes. Thus, extending the lifespan of permeable bricks is crucial for stabilizing production, improving product quality, and reducing production costs.

[0019] At present, the industry has mainly focused on improving the permeable bricks by addressing issues related to the material, shape, gas source, and process parameters of the permeable bricks. For example, improving the material of the permeable bricks, improving the shape of the bricks, arranging the assembly dimensions of the permeable bricks reasonably, stabilizing the gas source pressure, maintaining and managing the bottom blowing pipeline, accelerating the hot turnover of the ladle, and reducing the temperature drop of the ladle (see: [1] Liu Shaoqin, Liu Shuguang, Wang Shaohua. Bottom blowing argon permeable bricks for ladle [J]. Metal World, 2011(5):4.DOI:10.3969 / j.issn.1000-6826.2011.05.014. [2] Li Zhen. Research on the application process optimization of bottom blowing external permeable bricks for Jiuquan Iron and Steel Group's 120t ladle [J]. Gansu Metallurgy (05) [2023-11-07].). In addition, some designs use protective devices to add to the permeable bricks. For example, the patent document with publication number CN202752595U uses an air bag and a protective valve installed at the bottom of the steel ladle. When the air source pressure disappears, the gas pressure inside the permeable brick can be maintained to form a protective film.

[0020] In summary, existing research mainly focuses on analyzing and improving the materials, structure, process parameters, and protective devices of permeable bricks, while research on dedicated protective materials for permeable bricks is lacking. Through long-term practice, the inventors discovered that covering the surface of permeable bricks with a dedicated protective material while the ladle is empty can protect them from direct erosion and maintain their permeability, effectively improving their service life.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention is made by mixing granular raw materials such as magnesium aluminum spinel, fused refining slag, magnesia, white corundum and fluorite in a specific ratio, with a porosity of more than 15%, which effectively ensures the permeability of the permeable brick during the initial argon blowing.

[0023] 2. By using a combination of high- and low-melting-point raw materials and flux, and controlling the appropriate sintering temperature, the protective material undergoes surface sintering at the idle temperature of the ladle, while the interior remains loose. The resulting sintered shell prevents residual molten steel or slag from adhering to the surface of the permeable bricks during ladle movement. During the impact of the tapping steel flow, these residues are not directly washed away or instantly floated to the surface, thus preventing direct contact between the molten steel and the permeable bricks. This reduces the direct scouring of the permeable bricks by the molten steel during tapping, ensuring both the permeability of the permeable bricks and extending their service life. Statistics show that the service life of the permeable brick core and the entire material can be increased by more than 15%, significantly reducing the frequency of permeable brick replacement.

[0024] 3. This invention uses CaO-MgO-Al2O3 with low SiO2 as the main component, which does not react with Al and Ti in the molten steel, thus avoiding the burning loss of aluminum and / or titanium in the steel during the tapping process and preventing silicon contamination in the molten steel. At the same time, the protective material composed of this material can adsorb non-metallic inclusions such as S, Al2O3, and SiO2 in the steel during the mixing and floating process, thereby improving the cleanliness of the molten steel.

[0025] 4. The protective material of this invention is placed at the bottom of the ladle and is directly wrapped by the molten steel during tapping. It adopts a carbon-free design, which can effectively avoid the problem of carbon increase in molten steel caused by molten steel entrainment during tapping. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 Schematic diagram of external influencing factors during the use of breathable bricks. Detailed Implementation

[0028] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0029] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0030] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0031] Unless otherwise specified, all raw materials are derived from commercially available products and do not contain any unspecified components other than unavoidable impurities.

[0032] In this invention, the particle size of magnesium aluminum spinel, fused refining slag, magnesia, white corundum and fluorite are all 0.3-1.0 mm.

[0033] Magnesium aluminum spinel composition: MgO: 25.0-31.0%, Al2O3: 69.0-75.0%.

[0034] The composition of the fused refining slag is: SiO2≤3.0%, CaO:47.0-53.0%, Al2O3:37.0-43.0%.

[0035] Magnesia composition: MgO ≥ 97.0%.

[0036] White fused alumina composition: Al2O3≥99.0%.

[0037] Fluorite composition: SiO2≤6.0%, CaF2≥90.0%.

[0038] Example 1: Weigh 25 parts of magnesium aluminum spinel, 30 parts of fused refining slag, 20 parts of magnesia, 5 parts of white corundum, and 20 parts of fluorite. Use a double-layer sieve with an upper pore size of 1.0 mm and a lower pore size of 0.3 mm to screen and remove ash. Place the mixture in a mixer and stir for 20 minutes to mix evenly. Test the finished product. The test results are: SiO2 1.20%, CaO 15.70%, MgO 32.18%, Al2O3 30.30%, CaF2 18.15%, H2O 0.32%. The results meet the quality requirements and are packaged and stored.

[0039] Before tapping W60P ultra-low carbon high silicon high aluminum steel from the converter at Xichang Steel & Vanadium Company, the argon-blown material was evenly added to the permeable bricks through pipelines. The ladle temperature was 1100℃. After tapping, the steel reached the refining station. The permeable bricks showed good argon permeability, with a blowing rate of approximately 100%. Samples were taken and tested at the continuous casting station. The composition of the molten steel was normal, with no increase in Si, Al loss, or carbon. The content of non-metallic inclusions in the molten steel met the quality requirements, and the purity was good. The service life of the permeable brick core increased from 23 heats to 27 heats, an increase of 17.4%, and the overall service life of the permeable bricks increased from 45 heats to 54 heats, an increase of 20.0%.

[0040] Example 2: Weigh 20 parts of magnesium aluminum spinel, 60 parts of fused refining slag, 5 parts of magnesia, 5 parts of white corundum, and 10 parts of fluorite. Use a double-layer sieve with an upper pore size of 1.0 mm and a lower pore size of 0.3 mm to sieve and remove ash. Place the mixture in a mixer and stir for 20 minutes to mix evenly. Test the finished product. The test results are: SiO2 1.80%, CaO 3 1.05%, MgO 14.03%, Al2O3 3 2.16%, CaF2 18.34%, H2O 0.29%. The results meet the quality requirements and are packaged and stored.

[0041] Before tapping high-alumina steel W780QX (Al 0.5~0.75%) from the converter at Tangshan Iron and Steel, the argon permeability of the molten steel was uniformly added to the permeable bricks through pipelines. The ladle temperature was 900℃. After tapping, the molten steel reached the refining station. The permeable bricks showed good argon permeability with a blowing rate of about 100%. Samples were taken and tested at the continuous casting station. The composition of the molten steel was normal, with no increase in Si or loss of Al. The content of non-metallic inclusions in the molten steel met the quality requirements, and the purity was good. The service life of the permeable brick core increased from 24 heats to 28 heats, an increase of 16.7%, and the overall service life of the permeable bricks increased from 47 heats to 56 heats, an increase of 19.1%.

[0042] Example 3: Weigh 15 parts of magnesium aluminum spinel, 45 parts of fused refining slag, 15 parts of magnesia, 10 parts of white corundum, and 15 parts of fluorite. Use a double-layer sieve with an upper pore size of 1.0 mm and a lower pore size of 0.3 mm to screen and remove ash. Place the mixture in a mixer and stir for 20 minutes to mix evenly. Test the finished product. The test results are: SiO2 1.33%, CaO2 3.25%, MgO2 9.75%, Al2O3 29.46%, CaF2 13.73%, H2O 0.26%. The results meet the quality requirements and are packaged and stored.

[0043] Before tapping the 700XT (Ti 0.10~0.15%) titanium-containing automotive body steel from the converter at Chengde Iron & Steel Co., Ltd., the argon permeability of the molten steel was uniformly added to the permeable bricks through pipelines. The ladle temperature was 1000℃. After tapping, the molten steel reached the refining station. The permeable bricks showed good argon permeability with a blowing rate of approximately 100%. Samples were taken and tested at the continuous casting station. The composition of the molten steel was normal, with no increase in Si or loss of Ti. The content of non-metallic inclusions in the molten steel met the quality requirements, and the purity was good. The service life of the permeable brick core increased from 20 heats to 25 heats, an increase of 25.0%, and the overall service life of the permeable bricks increased from 40 heats to 51 heats, an increase of 27.5%.

[0044] Example 4: 10 parts of magnesium aluminum spinel, 53 parts of fused refining slag, 10 parts of magnesia, 15 parts of white corundum, and 12 parts of fluorite were weighed and sieved to remove ash using a double-layer sieve with an upper pore size of 1.0 mm and a lower pore size of 0.3 mm. The mixture was then placed in a mixer and stirred for 20 minutes to ensure uniform mixing. The finished product was tested, and the results were as follows: SiO2 1.42%, CaO 27.27%, MgO 28.61%, Al2O3 29.05%, CaF2 11.07%, and H2O 0.29%. The results met the quality requirements and the product was packaged and stored.

[0045] Before tapping 55SiCr steel at Xining Special Steel, the argon permeability of the molten steel was uniformly added to the permeable bricks through pipelines. The ladle was kept at an idle temperature of 1000℃. After tapping, the molten steel reached the refining station. The permeable bricks showed good argon permeability with a blowing rate of approximately 100%. Samples were taken and tested at the continuous casting station. The composition of the molten steel was normal, with no increase in Si, Al loss, or carbon. The content of non-metallic inclusions in the molten steel met the quality requirements, and the purity was good. The service life of the permeable brick core increased from 19 heats to 23 heats, an increase of 21.1%, and the overall service life of the permeable bricks increased from 37 heats to 46 heats, an increase of 24.3%.

[0046] Example 5: Weigh 30 parts of magnesium aluminum spinel, 35 parts of fused refining slag, 8 parts of magnesia, 12 parts of white corundum, and 15 parts of fluorite. Use a double-layer sieve with an upper pore size of 1.0 mm and a lower pore size of 0.3 mm to screen and remove ash. Place the mixture in a mixer and stir for 20 minutes to mix evenly. Test the finished product. The test results are: SiO2 1.15%, CaO 18.15%, MgO 23.95%, Al2O3 36.10%, CaF2 13.68%, H2O 0.30%. The results meet the quality requirements and are packaged and stored.

[0047] Before tapping the 60Si2Mn steel produced by Longteng Special Steel, the argon-blown material was evenly added to the permeable bricks through pipelines. The ladle was kept at an idle temperature of 1000℃. After tapping, the argon-blown material reached the refining station. The permeable bricks showed good argon permeability, with a blowing rate of approximately 100%. Samples were taken and tested at the continuous casting station. The composition of the molten steel was normal, with no increase in Si, Al loss, or carbon. The content of non-metallic inclusions in the molten steel met the quality requirements, and the purity was good. The service life of the permeable brick core increased from 20 heats to 23 heats, an increase of 15.0%, and the overall service life of the permeable bricks increased from 40 heats to 47 heats, an increase of 17.5%.

[0048] The following are comparative examples.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that the electrofused refining slag is omitted. The specific preparation method is as follows: 30 parts of magnesium aluminum spinel, 25 parts of magnesia, 15 parts of white corundum, and 30 parts of fluorite are weighed and screened to remove ash using a double-layer sieve with an upper pore size of 1.0 mm and a lower pore size of 0.3 mm. The mixture is then placed in a mixer and stirred for 20 minutes to mix evenly. The finished product is tested, and the test results are as follows: SiO2 0.9%, CaO 0.6%, MgO 47.88%, Al2O3 21.90%, CaF2 27.00%, H2O 0.30%.

[0051] Before tapping W60P ultra-low carbon high silicon high aluminum steel from the converter at Xichang Steel & Vanadium Company, the permeable bricks were evenly added through pipelines. The ladle temperature was 1100℃. After tapping, the permeable bricks reached the refining station. Initially, the permeability of the permeable bricks was good, but it was poor in the middle and later stages, with an overall blowing rate of about 80%. When samples were taken at the continuous casting station, the composition of the molten steel was normal, with no increase in Si, Al loss, or carbon. The content of non-metallic inclusions in the molten steel met the quality requirements, and the purity was good. The service life of the permeable bricks was not significantly improved.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 1 is that magnesia is omitted. The specific preparation method is as follows: 35 parts of magnesium aluminum spinel, 30 parts of fused refining slag, 15 parts of white corundum, and 20 parts of fluorite are weighed and screened to remove ash using a double-layer sieve with an upper pore size of 1.0 mm and a lower pore size of 0.3 mm. The mixture is then placed in a mixer and stirred for 20 minutes to mix evenly. The finished product is tested, and the test results are as follows: SiO2 1.20%, CaO 15.70%, MgO 25.53%, Al2O3 37.70%, CaF2 18.15%, H2O 0.32%.

[0054] Before tapping W60P ultra-low carbon high silicon high aluminum steel from the converter at Xichang Steel & Vanadium Company, the argon permeability of the molten steel was uniformly added to the permeable bricks through pipelines. The ladle temperature was 1100℃. After tapping, the molten steel reached the refining station. The argon permeability of the permeable bricks was generally average, with a blowing rate of about 85%. When the molten steel was sampled and tested at the continuous casting station, the composition of the molten steel was normal, with no increase in Si, Al loss, or carbon. The content of non-metallic inclusions in the molten steel met the quality requirements, and the purity was good. The service life of the permeable brick core increased from 23 heats to 25 heats, an increase of 8.7%, and the overall service life of the permeable bricks increased by about 9.0%.

[0055] In summary, the protective material specifically for permeable bricks provided by this invention can improve the air permeability of permeable bricks during use, increase their airflow rate, protect them from molten steel corrosion, extend their service life, and at the same time, it will not introduce pollution into the molten steel, thus having strong practical value.

[0056] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A breathable brick protective material, characterized in that: It is made from the following raw materials: 10-30 parts by weight of magnesium aluminum spinel, 30-60 parts by weight of fused refining slag, 5-20 parts by weight of magnesia, 5-15 parts by weight of white corundum, and 10-20 parts by weight of fluorite. The particle size of the magnesium aluminum spinel, fused refining slag, magnesia, white corundum, and fluorite is 0.3-1.0 mm. The selected magnesium aluminum spinel has the following composition: MgO: 25.0-31.0%, Al2O3: 69.0-75.0%; the fused refining slag has the following composition: SiO2≤3.0%, CaO: 47.0-53.0%, Al2O3: 37.0-43.0%; the magnesia has the following composition: MgO≥97.0%; the white corundum has the following composition: Al2O3≥99.0%; and the fluorite has the following composition: SiO2≤6.0%, CaF2≥90.0%.

2. The application of the permeable brick protective material as described in claim 1 in the refining of aluminum-containing, titanium-containing, or ultra-low carbon steel ladles, characterized in that: Before aluminum-containing, titanium-containing, or ultra-low carbon steel is tapped, the permeable bricks are evenly added through pipes to the upper surface of the steel, ensuring complete coverage.

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