Self-lubricating and self-repairing baking-free blind plate for tundish and preparation method thereof

Abstract

The application discloses a self-lubricating and self-repairing baking-free blind plate for a tundish and a preparation method thereof, and belongs to the field of shaped refractory materials. Raw material components are as follows: sintered tabular corundum aggregate, sintered tabular corundum fine powder, alpha-Al2O3 micro powder, metal silicon powder, metal aluminum powder, nano carbon black, Ti3AlC2 fine powder and phenolic resin. The preparation method is as follows: the sintered tabular corundum fine powder, alpha-Al2O3 micro powder, metal silicon powder, metal aluminum powder, nano carbon black and Ti3AlC2 fine powder are premixed in a high-speed stirrer, then the sintered tabular corundum aggregate is stirred in a low-speed stirrer and added with liquid phenolic resin, the premixed powder is continuously stirred, the mixed raw materials are pressure formed in a fixed-size mold by using a hydraulic machine, and solidification and heat treatment can be carried out. The application adds Ti3AlC2 with a layered self-repairing characteristic in the composition, the Ti3AlC2 has good self-lubricating and self-repairing characteristics at high temperatures, has high oxidation resistance and thermal shock resistance, and has higher use effect and service life compared with traditional corundum pouring material quality blind plates.

Description

Technical Field

[0001] This invention belongs to the field of shaped refractory materials and relates to a self-lubricating, self-repairing, non-burning blind plate for tundishes and its preparation method. Background Technology

[0002] To achieve continuous and stable production in the continuous casting tundish, technical personnel developed a rapid replacement technology for tundish sizing nozzles. When a nozzle reaches the end of its service life, a sliding mechanism between the tundish lower nozzle and the long nozzle, in conjunction with a tundish blind flange, slides to block the molten steel. Under protective casting conditions, the sizing nozzle, having reached the end of its service life, is replaced, ensuring the continuous casting speed remains stable within the required range without adversely affecting the molten steel flow in the tundish or the molten steel level in the crystallizer. During this process, the sliding of the nozzle and blind flange must be as smooth and rapid as possible, requiring high lubricity. However, due to the limited space under the tundish, the rapid nozzle replacement mechanism is open and lacks corresponding anti-oxidation measures. Currently, the tundish blind flanges used are mainly made of corundum castable, but due to their rough surface and lack of lubrication, the sliding resistance is very high, causing significant inconvenience. Although lubricant coatings can be applied to the sliding surface to ensure lubrication, high-temperature lubricants are expensive to prepare and have poor performance, resulting in high production costs and low efficiency.

[0003] In fact, researchers have conducted extensive work to address the poor oxidation resistance of traditional aluminum-carbon materials. On one hand, adding metallic antioxidants such as Si and Al protects the carbon raw materials from oxidation and promotes the formation of ceramic phases like SiC, Al4C3, and AlN, thus increasing material strength. However, this approach also presents challenges, such as excessive strength leading to decreased thermal shock resistance, the formation of Si-containing gas phases at high temperatures resulting in a porous structure, and the hydration of easily hydrated phases like Al4C3 and AlN causing a decrease in material strength. On the other hand, introducing nano-carbon sources (such as nano-carbon black, carbon nanotubes, and graphene oxide nanosheets) to replace traditional graphite as the carbon raw material helps resist slag and molten steel erosion and provides thermal shock resistance. The high specific surface area of ​​nano-carbon sources allows for continuous dispersion within the material at relatively low concentrations, preventing the formation of numerous pores after the oxidation of the carbon raw material, which would otherwise damage the material structure and reduce its strength. Nevertheless, the oxidation resistance of aluminum-carbon materials using the above measures is limited and still cannot meet the requirements for use in open mechanisms with quick-change nozzles in tundishes. In addition, the lubricity and thermal shock resistance of the material are significantly reduced after a large amount of flake graphite is replaced.

[0004] In recent years, researchers have introduced hexagonal boron nitride layered compounds into magnesium-carbon sliding plates, utilizing their high-temperature resistance, oxidation resistance, toughness, and lubrication properties to prepare self-lubricating magnesium slag-blocking sliding plate bricks (CN108585797A) with better high-temperature resistance, erosion resistance, scour resistance, and thermal shock stability. However, at high temperatures, the boron oxide formed by the oxidation of boron nitride easily forms a low-melting-point phase with magnesium oxide and silicon oxide, reducing the material's high-temperature performance. Furthermore, researchers have introduced ternary compounds such as aluminum silicon-carbon and titanium silicon-carbon into carbon-containing sliding plates, utilizing their oxidation to generate oxides such as SiO2, Al2O3, and TiO2 to fill pores, achieving self-repair and oxidation resistance, significantly improving the service life of these materials. However, the aforementioned carbon-containing sliding plates show a significant decrease in lubrication and thermal shock resistance due to the formation of a large amount of ceramic phase at high temperatures, and SiO2, as the main oxidation product of these ternary compounds, easily forms a glassy phase or a silicon-containing gas phase at high temperatures, leading to a decline in material performance. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to address the problems of poor lubrication and short service life of corundum blind plates. The aim is to provide an aluminum carbon blind plate (a self-lubricating, self-repairing, and burn-free blind plate for tundishes) with self-lubricating and self-repairing properties, which does not require high-temperature firing and has a long service life, as well as its preparation method.

[0006] Technical Solution: The present invention provides a self-lubricating, self-repairing, and non-sintering blind flange for intermediate ladles. The raw material composition and mass percentage of the aluminum-carbon blind flange are as follows: 60-70% sintered plate-shaped corundum aggregate, 15-25% sintered plate-shaped corundum fine powder, 5-15% α-Al2O3 micro powder, 1-5% metallic silicon powder, 2-8% metallic aluminum powder, 1-2% nano carbon black, 3-5% Ti3AlC2 fine powder, and 3-6% phenolic resin.

[0007] Furthermore, the raw material composition and mass percentage of the aluminum-carbon blind plate are as follows: 60% sintered plate-shaped corundum aggregate, 15% sintered plate-shaped corundum fine powder, 5% α-Al2O3 micro powder, 1% metallic silicon powder, 2% metallic aluminum powder, 1% nano carbon black, 3% Ti3AlC2 fine powder, and 3% phenolic resin.

[0008] Furthermore, the raw material composition and mass percentage of the aluminum-carbon blind plate are as follows: 70% sintered plate-shaped corundum aggregate, 25% sintered plate-shaped corundum fine powder, 15% α-Al2O3 micro powder, 5% metallic silicon powder, 8% metallic aluminum powder, 2% nano carbon black, 5% Ti3AlC2 fine powder, and 6% phenolic resin.

[0009] Furthermore, the raw material composition and mass percentage of the aluminum-carbon blind plate are as follows: 65% sintered plate-shaped corundum aggregate, 20% sintered plate-shaped corundum fine powder, 10% α-Al2O3 micro powder, 3% metallic silicon powder, 5% metallic aluminum powder, 1.5% nano carbon black, 4% Ti3AlC2 fine powder, and 4.5% phenolic resin.

[0010] Furthermore, the particle size of the sintered plate-shaped corundum aggregate is less than or equal to 3 mm.

[0011] Furthermore, the particle size of the sintered plate-shaped corundum fine powder is less than or equal to 0.088 mm.

[0012] Furthermore, the average particle size of the α-Al2O3 micro powder is 1–3 μm.

[0013] Furthermore, the Si content in the metallic silicon powder is greater than or equal to 98wt%, and the average particle size is 3-14μm. It mainly promotes the formation of ceramic phases such as SiC during high-temperature use and improves the strength of the material. However, too much Si can easily lead to excessive strength and the generation of silicon-containing gas phase, resulting in roughening of the blind plate and poor sealing and lubrication effect. Therefore, this invention controls it to 1-5%.

[0014] Furthermore, the aluminum powder contains an Al content of ≥98wt% and an average particle size of 3-14μm. After heat treatment at 600-800℃, a continuous liquid metal bonding phase is formed within the material, providing early strength. During high-temperature use, ceramic phases such as Al4C3 and AlN are also formed, which improves the material strength. However, excessive Al content can lead to excessive strength and hydration risk, resulting in poor sealing and lubrication of the blind plate and reduced lifespan. Therefore, this invention controls the Al content to 2-8%.

[0015] Furthermore, the carbon content in the nano-carbon black is greater than or equal to 99 wt%, and the average particle size is 50-900 nm. It mainly replaces traditional graphite as a carbon raw material to play a role in resisting slag and molten steel erosion and thermal shock. At the same time, as a nano-powder, it has a high specific surface area and can play a role in continuous dispersion in the material at a low content, which is beneficial to improving the oxidation resistance of the material. Therefore, the present invention controls it to 1-2%.

[0016] Furthermore, the Ti3AlC2 fine powder contains a Ti3AlC2 content greater than or equal to 95wt%, with an average particle size of 3-45μm. Ti3AlC2 has a hexagonal layered structure similar to flake graphite, and the layered structure can play a certain lubricating role through slippage and dislocation. In addition, the Al in the structure will preferentially oxidize to form stable alumina to fill the pores and play a self-healing and self-repairing role. After being introduced into the material, it mainly plays a self-lubricating and self-repairing role.

[0017] Furthermore, the phenolic resin is in liquid form, and the residual C content after high-temperature pyrolysis at 400-600℃ is greater than or equal to 30%.

[0018] Furthermore, a method for preparing a self-lubricating, self-repairing, non-sintering blind plate for intermediate ladle is described below: The sintered plate-shaped corundum fine powder, α-Al2O3 micro powder, metallic silicon powder, metallic aluminum powder, 1-2% nano-carbon black, and Ti3AlC2 fine powder are premixed in a high-speed mixer for 10-30 minutes. Then, the sintered plate-shaped corundum aggregate is stirred in a low-speed mixer, and liquid phenolic resin is added. Finally, the premixed powder is added, and mixing continues for 10-30 minutes until homogeneous. The mixed raw materials are then molded in a fixed-size mold using a hydraulic press at a pressure of 120-180 MPa, cured at 140-200℃ for 1-2 days, and then heat-treated at 600-800℃ for 3-5 hours.

[0019] Beneficial Effects: Compared with existing technologies, this invention introduces Ti3AlC2 into aluminum-carbon non-fired blind flanges. Its characteristics are: 1. This invention uses a metal-bonded aluminum-carbon material to replace corundum castable blind flanges, resulting in better lubrication performance, resistance to slag / molten steel erosion, and thermal shock resistance. Furthermore, traditional calcium aluminate-bonded corundum castables often require high-temperature firing at 1200–1400℃ for densification to ensure sufficient strength, while the metal-bonded aluminum-carbon material prepared in this invention only requires low-temperature heat treatment at 600–800℃, significantly reducing energy consumption; 2. Because Ti3AlC2 has a hexagonal layered structure similar to flake graphite, the aluminum-carbon non-fired blind flange prepared in this invention exhibits excellent self-lubricating properties during high-temperature use, improving the efficiency of the blind flange during sliding. 1. Reduces wear on the blind plate during sliding and improves its service life; 2. Due to the stable alumina filling the pores formed by Ti3AlC2 during high-temperature oxidation, it compensates for the loose structure caused by the formation of pores in the carbon raw material at high temperature, promotes densification and inhibits further oxidation of the material, so that the aluminum-carbon non-fired blind plate prepared by this invention has good self-healing properties and oxidation resistance when used at high temperature, which greatly improves the service life of the blind plate; 3. Due to the high thermal conductivity and layered structure of Ti3AlC2, it can play a role similar to graphite in relieving thermal stress when subjected to thermal shock at high temperature. The aluminum-carbon non-fired blind plate prepared by this invention has high thermal shock stability, and is safer and has a longer service life under the cold and hot shock caused by frequent contact and separation with molten steel. Detailed Implementation

[0020] The present invention will be further illustrated by specific embodiments below.

[0021] Comparative Example 1:

[0022] A corundum castable blind flange for tundishes, comprising the following raw materials and mass ratios: 72% sintered platy corundum aggregate (<5mm), 15% sintered platy corundum fine powder, 3% α-Al2O3 micro powder, 10% pure calcium aluminate cement, and 0.1% each of sodium hexametaphosphate and polycarboxylate water-reducing agent; 5.5% water is added to the castable, stirred evenly, molded, cured for 2 days, demolded, baked, and heat-treated at 1000℃ and 1400℃ for 3 hours respectively to obtain a common blind flange for tundishes.

[0023] The flexural strength of the blind flange after baking was 12.5 MPa. After low-temperature firing at 1000℃, the flexural strength was 5.9 MPa, showing a significant decrease in strength that failed to meet the usage requirements. After high-temperature firing at 1400℃, the flexural strength was 15.5 MPa, meeting the usage requirements. Industrial tests were conducted on an intermediate ladle at ~1530℃. After each test, the sliding surface was inspected. If there were no scratches on the sliding surface, it could continue to be used; if obvious scratches or cracks appeared, it was discontinued and replaced with the next set. Using the high-temperature lubricant prepared in this embodiment, 50 sets of industrial tests were conducted, with an average continuous sliding count of 1.0 times / set.

[0024] Example 1:

[0025] A self-lubricating and self-repairing blind flange for tundishes, comprising the following raw materials and their mass ratio: 60% sintered plate-shaped corundum aggregate, 20% sintered plate-shaped corundum fine powder, 7% α-Al2O3 micro powder, 1% metallic silicon powder, 8% metallic aluminum powder, 1% nano carbon black, 3% Ti3AlC2 fine powder (3-14μm), and 6% added phenolic resin. The sintered plate-shaped corundum fine powder, α-Al2O3 micro powder, metallic silicon powder, metallic aluminum powder, nano carbon black, and Ti3AlC2 fine powder are premixed in a high-speed mixer for 20 minutes. Then, the sintered plate-shaped corundum aggregate is stirred in a low-speed mixer, and liquid phenolic resin is added. Finally, the premixed powder is added, and mixing continues for 20 minutes until homogeneous. The mixed raw materials are then molded in a fixed-size mold using a hydraulic press at a pressure of 180MPa, cured at 200℃ for 2 days, and then heat-treated at 600℃ for 5 hours to obtain the self-lubricating blind flange for tundishes.

[0026] The flexural strength of the blind flange was tested to be 18.2 MPa, meeting the usage requirements. Industrial tests were conducted on an tundish at ~1530℃. After each test, the sliding surface was inspected; if no scratches were found, use continued; if obvious scratches or cracks appeared, use was discontinued and the next batch was replaced. Using the high-temperature lubricant prepared in this embodiment, 50 industrial tests were conducted, with an average of 4.5 consecutive sliding cycles per batch.

[0027] Example 2:

[0028] A self-lubricating and self-repairing blind flange for tundishes, comprising the following raw materials and their mass ratios: 70% sintered plate-shaped corundum aggregate, 10% sintered plate-shaped corundum fine powder, 6% α-Al2O3 micro powder, 5% metallic silicon powder, 2% metallic aluminum powder, 2% nano carbon black, 5% Ti3AlC2 fine powder (14-45μm), and 3% added phenolic resin. The sintered plate-shaped corundum fine powder, α-Al2O3 micro powder, metallic silicon powder, metallic aluminum powder, nano carbon black, and Ti3AlC2 fine powder are premixed in a high-speed mixer for 30 minutes. Then, the sintered plate-shaped corundum aggregate is stirred in a low-speed mixer, and liquid phenolic resin is added. Finally, the premixed powder is added, and mixing continues for 30 minutes until homogeneous. The mixed raw materials are then molded in a fixed-size mold using a hydraulic press at a pressure of 150MPa, cured at 140℃ for 1 day, and then heat-treated at 800℃ for 3 hours to obtain the self-lubricating blind flange for tundishes.

[0029] The flexural strength of the blind flange was tested to be 25.1 MPa, meeting the usage requirements. Industrial tests were conducted on an tundish at ~1530℃. After each test, the sliding surface was inspected; if no scratches were found, use continued; if obvious scratches or cracks appeared, use was discontinued and the next batch was replaced. Using the high-temperature lubricant prepared in this embodiment, 50 industrial tests were conducted, with an average of 3.6 consecutive sliding cycles per batch.

[0030] Example 3:

[0031] A self-lubricating and self-healing blind flange for intermediate tundishes, comprising the following raw materials and their mass ratio: 64% sintered plate-shaped corundum aggregate, 16% sintered plate-shaped corundum fine powder, 8% α-Al2O3 micro powder, 2% metallic silicon powder, 4% metallic aluminum powder, 2% nano carbon black, 2% Ti3AlC2 fine powder (3-14μm), 2% Ti3AlC2 fine powder (14-45μm), and 4.5% added phenolic resin; the sintered plate-shaped corundum fine powder and α-Al2O3 micro powder are... Metallic silicon powder, metallic aluminum powder, nano carbon black, and Ti3AlC2 fine powder are premixed in a high-speed mixer for 10 minutes. Then, sintered plate-shaped corundum aggregate is stirred in a low-speed mixer and liquid phenolic resin is added. Finally, the premixed powder is added and the mixture is stirred for another 10 minutes until uniform. The mixed raw materials are then molded in a fixed-size mold using a hydraulic press at a pressure of 120 MPa. The mixture is cured at 160℃ for 2 days and then heat-treated at 700℃ for 4 hours to obtain a self-lubricating blind plate for intermediate ladles.

[0032] The flexural strength of the blind flange was tested to be 22.4 MPa, meeting the usage requirements. Industrial tests were conducted on an tundish at ~1530℃. After each test, the sliding surface was inspected; if no scratches were found, use continued; if obvious scratches or cracks appeared, use was discontinued and the next batch was replaced. Using the high-temperature lubricant prepared in this embodiment, 50 industrial tests were conducted, with an average of 5.5 consecutive sliding cycles per batch.

[0033] Example 4:

[0034] A self-lubricating and self-repairing blind flange for intermediate tundishes, comprising the following raw materials and their mass ratio: 66% sintered plate-shaped corundum aggregate, 14% sintered plate-shaped corundum fine powder, 6% α-Al₂O₃ micro powder, 3% metallic silicon powder, 6% metallic aluminum powder, 1% nano carbon black, 2% Ti₃AlC₂ fine powder (3-14μm), 2% Ti₃AlC₂ fine powder (14-45μm), and 4% added phenolic resin; the sintered plate-shaped corundum fine powder, α-Al₂O₃ micro powder, ... Metallic silicon powder, metallic aluminum powder, nano carbon black, and Ti3AlC2 fine powder are premixed in a high-speed mixer for 25 minutes. Then, sintered plate-shaped corundum aggregate is stirred in a low-speed mixer and liquid phenolic resin is added. Finally, the premixed powder is added and the mixture is stirred for another 25 minutes until uniform. The mixed raw materials are then molded in a fixed-size mold using a hydraulic press at a pressure of 150 MPa. The mixture is cured at 180℃ for 1 day and then heat-treated at 700℃ for 5 hours to obtain a self-lubricating blind plate for intermediate ladle.

[0035] The flexural strength of the blind flange was tested to be 23.1 MPa, meeting the usage requirements. Industrial tests were conducted on an tundish at ~1530℃. After each test, the sliding surface was inspected; if no scratches were found, use continued; if obvious scratches or cracks appeared, use was discontinued and the next batch was replaced. Using the high-temperature lubricant prepared in this embodiment, 50 industrial tests were conducted, with an average of 5.1 consecutive sliding cycles per batch; details are shown in Table 1.

[0036] Table 1 Comparison of comparative examples and various embodiments

[0037]

[0038] This invention provides a self-lubricating, self-healing, burn-free blind flange for tundishes; the blind flange is composed of Ti3AlC2 with layered self-healing properties, which has good self-lubricating and self-healing properties at high temperatures, and has high anti-oxidation and thermal shock resistance. Compared with traditional corundum castable blind flanges, it has higher performance and service life.

Claims

1. A self-lubricating, self-healing, burn-free blind flange for intermediate tundishes, characterized in that, The raw material composition and mass percentage are as follows: 60-70% sintered plate corundum aggregate, 15-25% sintered plate corundum fine powder, 5-15% α-Al2O3 micro powder, 1-5% metallic silicon powder, 2-8% metallic aluminum powder, 1-2% nano carbon black, 3-5% Ti3AlC2 fine powder, and 3-6% phenolic resin. The particle size of the sintered plate-shaped corundum aggregate is ≤3mm; The particle size of the sintered plate-shaped corundum fine powder is ≤0.088mm; The average particle size of the α-Al2O3 micro powder is 1-3 μm; The silicon powder contains ≥98wt% Si and has an average particle size of 3-14μm. The aluminum powder contains ≥98wt% Al and has an average particle size of 3-14μm. The carbon black nanoparticles contain ≥99wt% C and have an average particle size of 50-900nm. The Ti3AlC2 fine powder contains ≥95wt% Ti3AlC2 and has an average particle size of 3-45μm. The phenolic resin is in liquid form, and the residual C content after high-temperature pyrolysis at 400-600℃ is ≥30%.

2. The method for preparing a self-lubricating, self-healing, burn-free blind flange for intermediate tundishes as described in claim 1, characterized in that, Its preparation process is as follows: (1): First, sintered plate-shaped corundum fine powder, α-Al2O3 micro powder, metallic silicon powder, metallic aluminum powder, nano carbon black and Ti3AlC2 fine powder are premixed in a high-speed mixer according to the proportion; The premixing time is 10 to 30 minutes. (2): Then, the sintered plate-shaped corundum aggregate is placed in a low-speed mixer and stirred while adding liquid phenolic resin and stirring continuously. (3): Next, add the premixed powder from step (1) to the mixture in step (2) and continue mixing until homogeneous; The mixing and stirring time is 10 to 30 minutes. (4): Finally, the raw materials mixed in step (3) are pressure-formed, cured and heat-treated in a fixed-size mold using a hydraulic press; The pressure in the mold is 120-180 MPa; The curing temperature is 140–200℃, and the time is 1–2 days. The heat treatment temperature is 600–800℃, and the time is 3–5 hours.

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