Continuous casting steel capillary hole ventilation rod head and preparation method thereof

Abstract

The invention discloses a continuous casting steel capillary hole ventilation rod head which comprises 12%-18% of white corundum, 34%-40% of fused alumina zirconia, 12%-14% of active a-Al 2O3 micro powder, 12%-14% of fused magnesite, 2%-4% of silicon carbide, 18%-22% of graphite, 1%-3% of olivine, 2%-4% of mica powder, 0.5%-1.5% of magnesium sulfate powder and 1.5%-2.5% of calcium sulfate. And the additional resin binder accounts for 14-16% of the total mass of the mixture. According to the continuous casting steel capillary hole ventilation rod head and the preparation method thereof, the argon flow is accurately controlled, the molten steel flow speed is accurately controlled, the molten steel quality is stable, the fluctuation condition of the liquid level of a crystallizer is improved, inclusion blockage is reduced, and the number of steel casting furnaces is increased.

Description

Technical Field

[0001] The present invention relates to the field of inorganic non-metallic refractory materials, and more particularly to a continuous casting steel capillary vent rod head and a preparation method thereof. Background Art

[0002] With the progress of technology, the requirements for the performance of steel are becoming increasingly stringent. Therefore, more and more varieties of steel have emerged, and the continuous casting processes of these steel grades are also becoming more and more demanding. It is required that continuous casting refractories not only meet the service life, but also have certain special use functions.

[0003] At present, the stopper rod heads for continuous casting of molten steel in tundishes at home and abroad are used to control the flow. Its function is the same as the principle of a valve, which can open and close the molten steel. However, the upper nozzle bowl of the tundish is used in cooperation with the stopper rod to control the flow of molten steel and the size of the molten steel flow. The service life of the stopper rod head determines its safety factor and service life. The surface of the stopper rod head is gradually eroded and deformed and shrunk after being washed by molten steel for a long time, bringing some potential hazards of flow control loss to the steel plant during steel pouring. At the same time, when the stopper rod head is washed to a certain limit value, the tundish must be replaced in advance, which affects the turnover time of the tundish, accelerates the consumption of refractories, affects the steelmaking rhythm, and reduces production capacity.

[0004] The effect diagram of the conventional argon-blowing stopper rod used in the current existing technology in cooperation with the upper nozzle of the tundish (as Figure 1 shown) basically meets the use requirements of the steel plant. However, sometimes during use, alumina deposits are adsorbed near the stopper rod head and the bowl of the upper nozzle of the tundish. As the molten steel flows downward, alumina inclusions in the steel billet are likely to occur, affecting the purity of the molten steel and causing nozzle blockage, bringing certain operation risks to production.

[0005] During the continuous casting production process of molten steel, the stopper rod head is a refractory material installed in the tundish to control the opening and closing of the nozzle and the flow of molten steel by lifting and displacement. The stopper rod head is a key functional refractory material in continuous casting steel production. The rod head cooperates with the upper nozzle of the tundish to control the molten steel flow from the tundish to the mold. Argon is blown into the molten steel flow channel through the stopper rod to prevent blockage due to inclusion deposition in the channel, improve the quality of molten steel, and maintain the normal progress of continuous casting production. Currently, the commonly used argon-blowing stopper rods mostly have single-hole or multi-hole argon-blowing stopper rod heads, and the vent holes are mostly straight-through large-aperture vent holes, while the invented product has curved micro-hole vent holes. During the continuous casting of molten steel, multiple furnaces are continuously poured, and the tundish uses the stopper rod head to control the flow. The stopper rod includes a rod body and a rod head. As the casting time prolongs, during the casting process, high-melting-point impurities will form in the molten steel, and these impurities will adhere to the outer layer of the stopper rod head during the casting process, seriously affecting the flow control accuracy of the stopper rod head. Summary of the Invention

[0006] To solve the above problems, an object of the present invention is to provide a continuous casting steel capillary vent rod head that can accurately control the argon gas flow rate, precisely control the molten steel flow rate, has stable molten steel quality, improves the fluctuation of the mold liquid level, reduces inclusion blockage, and increases the number of ladle pourings, and a preparation method thereof.

[0007] According to one aspect of the present invention, there is provided a continuous casting steel capillary vent rod head, comprising: 12%-18% white fused alumina, 34%-40% zirconium corundum, 12%-14% active a-Al2O3 micropowder, 12%-14% fused magnesia, 2%-4% silicon carbide, 18%-22% graphite, 1%-3% olivine, 2%-4% mica powder, 0.5%-1.5% magnesium sulfate powder, and 1.5%-2.5% calcium sulfate, and an additional resin binder is 14%-16% of the total mass of the above mixture.

[0008] In some embodiments, the Al2O3 content in the white fused alumina is ≥99.3%, and the SiO2 content is ≤0.05%;

[0009] The Al2O3 content in the zirconium corundum is 55%, and the ZrO2 content is 44%;

[0010] The MgO content in the fused magnesia is ≥97%;

[0011] The SiC content in the silicon carbide is ≥98%;

[0012] The C content in the graphite is ≥98%;

[0013] The (Mg,Fe)2SiO4 content in the olivine is 92%-88%;

[0014] The Al2O3 content in the mica powder is 30%, the K2O+Na2O content is 10%, and the SiO2 content is 45%.

[0015] In some embodiments, the particle size distribution of the white fused alumina is: 3-1mm, 2-1mm, 1-0mm, 0.5-0mm;

[0016] The particle size distribution of the zirconium corundum is: 3-1mm, 2-1mm, 1-0mm, 0.5-0mm;

[0017] The particle size distribution of the active a-Al2O3 micropowder is: 200 mesh;

[0018] The particle size distribution of the fused magnesia is: 325 mesh;

[0019] The particle size distribution of the silicon carbide is: 180 mesh;

[0020] The particle size distribution of the graphite is: 200 mesh;

[0021] The particle size distribution of the olivine is: 200 mesh;

[0022] The particle size distribution of the mica powder is: 200 mesh;

[0023] The particle size distribution of the magnesium sulfate powder is: 200 mesh;

[0024] The particle size distribution of the calcium sulfate is: 180 mesh;

[0025] The resin binder is a liquid.

[0026] In some embodiments, the ratio of the above-mentioned component particles to the fine powder is: particles∶fine powder = 6∶4.

[0027] According to one aspect of the present invention, there is provided a method for preparing a continuous casting steel capillary vent rod head. The method for preparing a continuous casting steel capillary vent rod head is characterized by comprising the following steps:

[0028] S1. Raw material selection;

[0029] S2. Batching, weighing and adding each group of batching according to the ratio;

[0030] S3. Mixing, using a planetary stirring device to stir and mix the raw materials evenly;

[0031] S4. Inspection, determining the particle size and moisture content of the mixed raw materials;

[0032] S5. Molding, adding raw materials into a mold and pressing them into a green body by a 2000-ton hydraulic press;

[0033] S6. Drying, drying the molded vent rod head green body;

[0034] S7. Firing, pushing the vent rod head green body into a high-temperature tunnel kiln for firing, and taking it out of the kiln after cooling to room temperature;

[0035] S8. Processing, processing the outer wall of the vent rod head to obtain standard inner and outer dimensions;

[0036] S9. Inspection, inspecting the appearance, dimensions, physical and chemical indexes, X-ray flaw detection and air vent detection of the finished product;

[0037] S10. Packing the qualified products into storage and destroying the unqualified products.

[0038] In some embodiments, in S5, cold isostatic pressing adopts a low-pressure molding process, the pressure is 45.0 MPa - 48.0 MPa, and at the same time, the raw materials need to be pressed while maintaining a constant temperature and humidity state, and the cold isostatic pressing time is 2 minutes.

[0039] In some embodiments, the drying in step S6 includes natural drying and heat drying. The natural drying is carried out at room temperature above 15°C for more than 6 hours, and the heat drying is carried out in a heating kiln at 175°C - 185°C for 24 hours.

[0040] In some embodiments, the firing in step S7 is carried out in a high-temperature tunnel, and the temperature is uniformly increased to 880°C - 920°C within 4 - 6 hours, then high-temperature fired for 8 - 12 hours, and then naturally cooled to room temperature.

[0041] A continuous casting steel capillary venting stopper head disclosed by the present invention has the beneficial effects of accurately controlling the argon flow rate, precisely controlling the steel water flow rate, stable steel water quality, improving the fluctuation of the mold liquid level, reducing clogging of inclusions, and increasing the number of ladle pourings. By adjusting the formula of the stopper head, the stopper head of the stopper rod adheres and peels off during long-term use; by forming an argon air curtain flow through the venting flow rate in the circumferential direction of the capillary pores formed on the stopper head to blow the alumina accumulation on the stopper head of the stopper rod and the tundish bowl mouth, the effect of preventing the nozzle from being blocked is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is an effect diagram of the conventional argon-blowing stopper rod used in the prior art in cooperation with the upper nozzle of the tundish;

[0043] Figure 2 is a schematic diagram of the use state of the continuous casting steel capillary venting stopper head of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The present invention will be described in detail below with reference to the embodiments shown in the drawings. However, it should be noted that these embodiments are not limitations on the present invention, and any equivalent transformation or substitution in terms of function, method, or structure made by those of ordinary skill in the art according to these embodiments shall fall within the protection scope of the present invention.

[0045] In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two components. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific situations.

[0046] During the continuous casting of molten steel, the stopper rod head is a refractory material installed in the tundish that controls the opening and closing of the water inlet and the flow of molten steel by lifting and displacing. The stopper rod head is a key functional refractory material in continuous steel casting production. The rod head cooperates with the upper water inlet of the tundish to control the steel flow from the tundish to the crystallizer. Argon is blown into the steel flow channel through the stopper rod to prevent the channel from being blocked by inclusion deposition, improve the quality of molten steel, and maintain the normal continuous casting production. At present, the commonly used argon blowing stopper rods are mostly single-hole or multi-hole argon blowing stopper rod heads, and the air holes are mostly straight-through large-aperture air holes, while the invented product is a curved micro-pore air hole. During the continuous casting of molten steel, multiple furnaces are continuously poured, and the tundish uses a stopper rod head for flow control. The stopper rod includes a rod body and a rod head. As the casting time increases, high-melting-point impurities will form in the molten steel during the pouring process. These impurities will adhere to the outer layer of the stopper rod head during the pouring process, seriously affecting the accuracy of the stopper rod head flow control.

[0047] A continuous casting steel capillary ventilation rod head comprises: 12%-18% white corundum, 34%-40% zirconium corundum, 12%-14% active a-Al2O3 micro powder, 12%-14% fused magnesia, 2%-4% silicon carbide, 18%-22% graphite, 1%-3% olivine, 2%-4% mica powder, 0.5%-1.5% magnesium sulfate powder and 1.5%-2.5% calcium sulfate, and an external resin binder accounts for 14%-16% of the total mass of the above mixture.

[0048] Through such a component, a curved capillary can be formed at the rod head, thereby realizing the ventilation of the rod head. The problem that the existing plug rod head in the prior art cannot well control the flow rate of argon gas, resulting in the rod head being unable to accurately control the flow rate of molten steel, causing eddy currents in the molten steel in the nozzle, and the unstable state of the eddy currents affecting the quality of the molten steel is solved.

[0049] The Al2O3 content in white corundum is ≥99.3%, and the SiO2 content is ≤0.05%. White corundum has excellent high-temperature stability, can maintain physical and chemical stability for a long time in a high-temperature environment, and is not easy to melt or deform.

[0050] The Al2O3 content of zirconium corundum is 55% and the ZrO2 content is 44%. Zirconium corundum can maintain stable performance in high temperature or even ultra-high temperature environment, and is not easy to deform or melt. Zirconium corundum can effectively extend the service life of refractory materials with its excellent corrosion resistance. In high temperature environment, zirconium corundum can still maintain a stable structure and is not easy to crack or peel off.

[0051] The MgO content in fused magnesia is ≥97%; fused magnesia can withstand high temperature and acid and alkali corrosion.

[0052] The SiC content in silicon carbide is ≥98%; silicon carbide has high refractoriness and good chemical stability.

[0053] The carbon content in graphite is ≥98%; graphite has extremely high heat resistance, with a maximum temperature of up to 3850°C, small mass loss in ultra-high temperature electric arcs, an anisotropic structure, a small linear expansion coefficient, good thermal shock resistance, and can remain stable in extremely cold and hot environments. Graphite also has good thermal conductivity and corrosion resistance.

[0054] The content of (Mg,Fe)2SiO4 in olivine is 92%-88%; olivine, as a key silicate mineral, contains components such as silicon dioxide, magnesium oxide, and iron oxide, enabling olivine to maintain the integrity and stability of its structure in high-temperature environments, thereby significantly enhancing the fire resistance of materials. At the application level, olivine not only enhances the compressive and abrasion resistance of refractory materials but also greatly improves the crack resistance of materials.

[0055] The content of Al2O3 in mica powder is 30%, the content of K2O + Na2O is 10%, and the content of SiO2 is 45%. The role of mica powder in refractory materials is mainly reflected in improving the thermal shock resistance and mechanical strength of materials.

[0056] Active a-Al2O3 fine powder can significantly improve the refractoriness of refractory materials. In high-temperature environments, α-Al2O3 fine powder will undergo ceramization and mullitization reactions, further enhancing the refractoriness of refractory materials. Active a-Al2O3 fine powder can enhance the strength and slag corrosion resistance of refractory materials. In addition, the addition of α-Al2O3 fine powder can reduce the porosity of castables and optimize the internal structure, thereby improving their refractory properties.

[0057] The functions of magnesium sulfate powder in refractory materials mainly include improving the refractoriness of refractory materials, the erosion resistance to alkaline slag and iron slag, and not polluting molten steel. Specifically, when magnesium sulfate is used as an adhesive, it can reduce the adverse effects caused by traditional adhesives such as silica fine powder, aluminate cement, or polyphosphates at high temperatures, such as liquid phase and phosphorus increase in molten steel problems, thereby improving the slag resistance and refractory properties of refractory materials.

[0058] Calcium sulfate will decompose and release crystal water at high temperatures, absorbing a large amount of heat, thereby reducing the temperature of the surrounding environment and delaying the combustion reaction. In addition, the carbon layer formed by calcium sulfate during the combustion process has good heat insulation and oxygen isolation properties.

[0059] The particle size distribution of white fused alumina is: 3-1mm, 2-1mm, 1-0mm, 0.5-0mm;

[0060] The particle size distribution of the zirconium corundum is: 3-1mm, 2-1mm, 1-0mm, 0.5-0mm;

[0061] The particle size distribution of the active a-Al2O3 fine powder is: 200 mesh;

[0062] The particle size distribution of the fused magnesia is: 325 mesh;

[0063] The particle size distribution of the silicon carbide is: 180 mesh;

[0064] The particle size distribution of the graphite is: 200 mesh;

[0065] The particle size distribution of the olivine is: 200 mesh;

[0066] The particle size distribution of the mica powder is: 200 mesh;

[0067] The particle size distribution of the magnesium sulfate powder is: 200 mesh;

[0068] The particle size distribution of the calcium sulfate is: 180 mesh;

[0069] The resin binder is a liquid.

[0070] The ratio of the above-mentioned various component particles to fine powder is: particles∶fine powder = 6∶4.

[0071] During the test, it was found that when the ratio of particles to fine powder is different, it will cause difficulty in forming capillary pores after firing or excessive capillary pores, resulting in erosion of the said rod head.

[0072] According to one aspect of the present invention, there is provided a method for preparing a continuous casting steel capillary aeration rod head. The method for preparing a continuous casting steel capillary aeration rod head is characterized by comprising the following steps:

[0073] S1. Raw material selection;

[0074] S2. Batching, weighing and adding each group of batching according to the ratio;

[0075] S3. Mixing, using a planetary stirring device to stir and mix the raw materials evenly;

[0076] S4. Inspection, determining the particle size and moisture content of the mixed raw materials;

[0077] S5. Molding, adding raw materials into a mold and pressing into a green body with a 2000-ton hydraulic press;

[0078] S6. Drying, drying the formed aeration rod head green body;

[0079] S7. Firing, pushing the aeration rod head green body into a high-temperature tunnel kiln for firing, and taking it out of the kiln after cooling to room temperature;

[0080] S8. Processing, processing the outer wall of the aeration rod head to obtain standard internal and external dimensions;

[0081] S9. Inspection, inspecting the appearance, dimensions, physical and chemical indexes, X-ray flaw detection and air permeability detection of the finished product;

[0082] S10. Pack the qualified products into storage and destroy the unqualified products.

[0083] In the said S5, cold isostatic pressing adopts a low-pressure forming process with a pressure of 45.0 MPa - 48.0 MPa. At the same time, the raw materials need to be pressed while maintaining a constant temperature and humidity state, and the cold isostatic pressing duration is 2 minutes.

[0084] The drying in the said S6 step includes natural drying and heating drying. The natural drying is carried out at room temperature above 15°C for more than 6 hours, and the heating drying is carried out in a heating kiln at 175°C - 185°C for 24 hours.

[0085] In the said S7 step, the firing is carried out in a high-temperature tunnel, and the temperature is uniformly raised to 880°C - 920°C within 4 - 6 hours, then high-temperature fired for 8 - 12 hours, and then naturally cooled to room temperature.

[0086] Through use tests, the specific situation is as follows in the table:

[0087]

[0088]

[0089] The actual effect after disassembly: It overcomes the original situation where due to the use of ordinary straight-hole argon-blowing plug rod heads, serious caking occurred at the upper tundish nozzle and the head of the plug rod, and the maximum number of ladles that could be cast was 10. Now, capillary hole plug rod heads are used for casting. Currently, the maximum number of ladles that can be cast is 16. The back pressure and opening are stable. After being taken offline, the head of the rod is relatively smooth, without obvious erosion and caking.

[0090] As Figure 2 shown, through the uniform distribution of the argon gas flow, the present invention can effectively prevent the accumulation of alumina substances at the rod head, the upper tundish nozzle bowl mouth and the bowl part, and the clogging of the nozzle, reduce the unstable back pressure of the plug rod, reduce the inclusion of foreign substances in the cast slab, and at the same time can extend the continuous casting life of the tundish.

[0091] Moreover, through the curved capillary vent rod head of the present invention, the problem of concentrated blowing in the conventional technology is eliminated, ensuring that argon gas can be diffused into the molten steel through the air permeable channels of the porous material at one time, forming small and uniform bubbles, eliminating the influence of large bubbles on the liquid level fluctuation in the mold, and removing impurities on the plug rod head, improving the flow control accuracy, and greatly enhancing the argon blowing effect.

[0092] Through multiple curved capillary air permeable channel rod heads, the channels are diffusely distributed in the head and inner wall areas of the rod head, improving the size and distribution state of the argon gas bubbles entering the molten steel, and adsorbing and removing inclusions and improving the nozzle caking effect through the tiny diffused argon bubbles.

[0093] Since the outlet directions of the multiple curved blowing capillary air permeation channels have components in all directions along the rod head, and the multiple blowing channels face the same circumferential direction, bubbles rotating around the rod head are formed around the rod head, driving the molten steel around to rotate, which can better clean the attachments inside the nozzle.

[0094] The outlet directions of the multiple curved blowing capillary air permeation channels have components in all directions along the rod head. In addition to having a circumferential component, the outlet direction of the blowing branch also has a downward axial component, which can make the argon stay in the molten steel for a longer time and have more sufficient contact.

[0095] The above are only some embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the creative concept of the present invention, other deformations and improvements can also be made, and these all belong to the protection scope of the present invention.

Claims

1. Continuously cast steel capillary pore ventilation rod head, characterized in that: Calculated by weight percentage, it includes: 12%-18% white corundum, 34%-40% zirconium corundum, 12%-14% active a-Al2O3 micropowder, 12%-14% fused magnesia, 2%-4% silicon carbide, 18%-22% graphite, 1%-3% olivine, 2%-4% mica powder, 0.5%-1.5% magnesium sulfate powder and 1.5%-2.5% calcium sulfate, and the added resin binder accounts for 14%-16% of the total mass of the above mixture.

2. The continuous casting steel capillary pore ventilation rod head according to claim 1, characterized in that: The Al2O3 content of the white corundum is ≥99.3%, and the SiO2 content is ≤0.05%; The Al2O3 content in the zirconium corundum is 55%, and the ZrO2 content is 44%; The MgO content in the fused magnesia is ≥ 97%; The SiC content in the silicon carbide is ≥ 98%; The C content in the graphite is ≥ 98%; The content of (Mg, Fe)2SiO4 in the olivine is 92%-88%; The mica powder contains 30% Al2O3, 10% K2O+Na2O and 45% SiO2.

3. The continuous casting steel capillary pore ventilation rod head according to claim 2, characterized in that: The particle size distribution of the white corundum is: 3-1mm, 2-1mm, 1-0mm, 0.5-0mm; The particle size distribution of the zirconium corundum is: 3-1mm, 2-1mm, 1-0mm, 0.5-0mm; The particle size distribution of the active a-Al2O3 powder is: 200 mesh; The particle size distribution of the fused magnesia is: 325 mesh; The particle size distribution of the silicon carbide is: 180 mesh; The particle size distribution of the graphite is: 200 mesh; The particle size distribution of the olivine is: 200 mesh; The particle size distribution of the mica powder is: 200 mesh; The particle size distribution of the magnesium sulfate powder is: 200 mesh; The particle size distribution of the calcium sulfate is: 180 mesh; The resin binder is liquid.

4. The continuous casting steel capillary pore ventilation rod head according to claim 3, characterized in that: The ratio of the particles to the fine powder of the above components is: particles: fine powder = 6:

4.

5. The method for preparing the continuous casting steel capillary pore ventilation rod head according to claim 4, characterized in that: The following steps are involved: S1. Raw material selection; S2, ingredients, add each group of ingredients according to the proportion; S3, mixing, using planetary mixing equipment to mix the raw materials evenly; S4. Check and determine the particle size and moisture content of the mixed raw materials; S5, forming, adding raw materials into the mold and pressing into a green body using a 2000-ton hydraulic press; S6, drying, drying the formed ventilation rod head blank; S7, firing, pushing the ventilated rod head blank into a high-temperature tunnel kiln for firing, and then cooling to room temperature before taking it out of the kiln; S8, processing, processing the outer wall of the ventilation rod head to obtain standard inner and outer dimensions; S9. Inspection: Check the appearance, size, physical and chemical indicators, X-ray flaw detection and ventilation of the finished product; S10. Qualified products are packaged and put into storage, and unqualified products are destroyed.

6. The method for preparing the continuous casting steel capillary pore ventilation rod head according to claim 5, characterized in that: In S5, the cold isostatic pressing adopts a low-pressure molding process with a pressure of 45.0 MPa-48.0 MPa. At the same time, the raw materials need to be pressed at a constant temperature and humidity. The cold isostatic pressing time is 2 minutes.

7. The method for preparing the continuous casting steel capillary pore ventilation rod head according to claim 5, characterized in that: The drying in step S6 includes natural drying and heating drying. The natural drying is drying at room temperature above 15°C for more than 6 hours, and the heating drying is drying in a heating kiln at 175°C-185°C for 24 hours.

8. The method for preparing the continuous casting steel capillary pore ventilation rod head according to claim 5, characterized in that: The firing in the step S7 is carried out by uniformly heating the temperature to 880° C.-920° C. in a high-temperature tunnel within 4-6 hours, firing at high temperature for 8 hours-12 hours, and then naturally cooling to room temperature.

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