Combined structure for improving sealing performance of long nozzle bowl of continuous casting and control method

Abstract

This invention relates to a combined structure and control method for improving the sealing performance of the bowl section of a long nozzle in continuous casting, belonging to the field of continuous casting technology in the metallurgical industry. The technical solution is as follows: a ladle (1), a ladle slide plate (2), a long nozzle (4), and a ladle outlet (6). The inner cavity of the long nozzle (4) includes a bowl-shaped inner cavity and a cylindrical inner cavity. A stepped platform (9) is formed between the bowl-shaped inner cavity and the cylindrical inner cavity. A high-temperature fiber flat pad (5) that cooperates with the ladle outlet (6) is provided on the stepped platform (9). A high-temperature fiber bowl pad (3) that cooperates with the ladle outlet (6) and an argon gas pipeline (10) that enters the bowl-shaped inner cavity are provided in the bowl-shaped inner cavity. The beneficial effects of this invention are: it can effectively improve the sealing stability of the bowl section of the long nozzle and the ladle outlet, prevent slag adhesion in the bowl section of the long nozzle, ensure the smooth flow of argon gas and the argon blowing effect, significantly improve the purity of molten steel, reduce the defect rate of the cast billet, and meet the requirements of high-end steel continuous casting production for the purity of molten steel.

Description

Technical Field

[0001] This invention relates to a combined structure and control method for improving the sealing performance of the long nozzle bowl in continuous casting, belonging to the field of continuous casting technology in the metallurgical industry. Specifically, it is applied to the sealing and protection of the long nozzle between the ladle and tundish during continuous casting, and is suitable for continuous casting production sites where high purity of molten steel is required for various aluminum deoxidized steels and ultra-low carbon steels. Background Technology

[0002] In recent years, as the steel industry has transformed towards high-end and refined products, downstream industries such as automobiles, high-end home appliances, and precision machinery have placed stringent demands on steel quality, especially on the precision required for controlling inclusion and gas content. Among these, aluminum-deoxidized steel, a core category of high-end steel, requires strict control of its aluminum content within a reasonable range. During continuous casting, aluminum readily reacts with oxygen in the air to form Al2O3 inclusions. These inclusions not only reduce the purity of the molten steel and affect the internal and surface quality of the billet, but in severe cases, they can also lead to nozzle formation and casting interruptions, directly impacting production, increasing costs, and hindering the release of high-end steel production capacity and the improvement of product competitiveness.

[0003] In continuous casting, the long nozzle, as the core connecting component between the ladle and the tundish, plays a crucial role in ensuring the airtight transport of molten steel, preventing secondary oxidation and splashing, and guaranteeing the safety and stability of the casting process. However, due to the hard contact fit between the long nozzle and the ladle's lower nozzle under high-temperature conditions, a tiny gap inevitably exists between them. This gap becomes the primary channel for air intrusion into the molten steel. During high-speed flow of molten steel, according to Bernoulli's principle in fluid mechanics, a negative pressure is generated in the gap region. The faster the molten steel flows, the greater the negative pressure becomes, easily drawing in outside air, which reacts with the molten steel and degrades its purity. This problem has become a key bottleneck restricting the effectiveness of continuous casting protection and improving billet quality.

[0004] To address the aforementioned issues, metallurgical scholars and enterprises both domestically and internationally have conducted extensive research, with a core focus on argon-sealing technology. This involves creating an argon-protected environment at the gap between the long nozzle and the ladle's bottom nozzle, ensuring that the gas drawn in under negative pressure is inert argon, thus preventing air from contacting the molten steel and improving the protective casting effect. Currently, existing argon-sealing technologies primarily focus on optimizing the sealing gasket structure of the long nozzle bowl and improving the argon blowing structure. However, due to the harsh environment of continuous casting (steel temperatures can reach 1500-1600℃), abundant dust and slag, and the shaking of the ladle turret, existing technologies generally suffer from poor sealing performance. For example, Chinese patent application No. 202410596546.1 discloses a continuous casting long nozzle argon sealing structure, argon blowing control system and control process. It achieves sealing by setting an annular groove on the outer periphery of the long nozzle bowl and introducing argon gas. However, the long nozzle bowl and the ladle lower nozzle are in conical contact fit. During the ladle tumbler process, shaking is inevitable, which leads to unstable contact gap between the two. In addition, the argon gas outlet is designed to be open to the outside, which makes it easy for argon gas to leak. It is difficult to form a stable argon gas protective atmosphere, and the sealing effect is greatly reduced. Secondly, Chinese patent application No. 201310640620.7 discloses a casting protection device and control method for a continuous casting ladle. It mainly involves opening a horizontal annular groove on the upper part of the inner cavity of the long nozzle at the connection between the long nozzle and the ladle's bottom nozzle. The horizontal annular groove is connected to an argon gas inlet pipe. The argon gas supply pipeline is equipped with an automatic regulating valve and a PID controller. However, the annular groove is easily blocked by the pressure of the sealing gasket, causing the argon gas channel to fail and making it impossible to achieve effective sealing. Moreover, the hard contact fit method cannot adapt to the positional deviation caused by the swaying of the rotary table, resulting in poor sealing reliability. Chinese patent application No. 202122160579.6 discloses a sealing device for the long nozzle of a continuous casting machine ladle. It mainly consists of a support base and a long nozzle set on the support base. The support base has an annular structure and corresponds to the position of the ladle nozzle. Two cylinders are symmetrically arranged on the inner wall of the annulus. The piston rod end of the cylinder is provided with an annular seal. The inner diameter of the two semi-annular seals is adapted to the outer diameter of the ladle nozzle after they are engaged. The support base, semi-annular seals, long nozzle and ladle nozzle together form a sealing cavity. The device has a complex structure, is complicated to operate, is not very practical, and is difficult to implement under harsh conditions such as high temperature.

[0005] Furthermore, existing technologies do not consider the impact of slag adhesion at the long nozzle bowl on the sealing effect. During continuous casting, steel slag easily adheres to the inner wall of the long nozzle bowl, resulting in a loose seal and further exacerbating argon leakage and air intrusion. Simultaneously, existing sealing structures are mostly single-seal designs, lacking a dual-protection mechanism. Once a single seal fails, it cannot be repaired in time, easily leading to secondary oxidation of molten steel, making it difficult to meet the requirements of continuous and stable production of high-end steel. Therefore, developing a sealing device and control method for the long nozzle bowl in continuous casting that is simple in structure, easy to operate, provides stable sealing, is adaptable to harsh on-site environments, effectively avoids slag adhesion, and provides dual protection has become an urgent technical challenge to be solved in the field of continuous casting technology in the metallurgical industry. Summary of the Invention

[0006] The purpose of this invention is to provide a combined structure and control method for improving the sealing performance of the long nozzle bowl in continuous casting. This structure can effectively improve the sealing stability of the long nozzle bowl and the ladle nozzle, prevent slag adhesion in the long nozzle bowl, ensure unobstructed argon passage and argon blowing effect, significantly improve the purity of molten steel, reduce the defect rate of cast billets, and meet the requirements of high-end steel continuous casting production for molten steel purity.

[0007] The technical solution of this invention is: A combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle, comprising a ladle, a ladle slide plate, a long nozzle, and a ladle outlet, characterized in that: the inner cavity of the long nozzle includes a bowl-shaped inner cavity and a cylindrical inner cavity, with a stepped platform formed between the bowl-shaped inner cavity and the cylindrical inner cavity; a high-temperature fiber flat gasket that mates with the ladle outlet is provided on the stepped platform; and a high-temperature fiber bowl gasket that mates with the ladle outlet and an argon gas pipeline leading into the bowl-shaped inner cavity are provided in the bowl-shaped inner cavity.

[0008] The bowl-shaped inner cavity of the long water inlet is provided with a groove in the circumferential direction that is connected to the argon gas pipeline, and a flow back pressure gauge is installed on the argon gas pipeline.

[0009] The inner cavity groove of the long water inlet bowl is a downward-sloping annular groove.

[0010] The downward inclination angle of the groove in the inner cavity of the long water spout bowl is 12-18°.

[0011] The width of the stepped platform formed between the inner cavity of the bowl and the inner cavity of the column is 1.5-2cm.

[0012] The depth of the bowl-shaped cavity of the long water inlet is 0.5-2cm greater than the distance between the end of the ladle water outlet and the steel plate slide.

[0013] The high-temperature fiber bowl pad is provided with a bowl edge that matches the ladle slide plate.

[0014] A control method for improving the sealing performance of the long nozzle bowl in continuous casting employs a combined structure for improving the sealing performance of the long nozzle bowl as defined above. During the casting process, the argon flow rate is dynamically adjusted according to the steel pouring volume, steel grade characteristics, and molten steel flow rate to ensure that the argon gas in the inner cavity of the long nozzle bowl is in a slightly positive pressure state.

[0015] During the casting process, the high-temperature fiber flat gasket squeezes the stepped platform of the long nozzle bowl cavity through the ladle's lower nozzle, thus sealing it and keeping the inner wall of the bowl cavity smooth. At the same time, argon gas is introduced into the inner cavity of the long nozzle bowl cavity to ensure that the inner cavity of the long nozzle bowl cavity is in a state of complete argon gas protection.

[0016] The beneficial effects of this invention are: 1. Dual sealing design for stable and reliable sealing effect: Through the synergistic cooperation of high-temperature fiber flat gasket and high-temperature fiber cup gasket, two sealing defenses are formed. It can achieve basic sealing through surface-to-surface contact compression, and can achieve complete sealing through cup gasket when the first seal fails, effectively preventing air intrusion and solving the problem of insufficient reliability of traditional single sealing structure. 2. Anti-slag adhesion and anti-clogging, suitable for harsh on-site environments: The annular groove of the long nozzle bowl is designed with the opening facing downward to prevent steel slag and impurities from clogging the argon gas channel; the high-temperature fiber flat gasket can prevent slag adhesion to the long nozzle bowl, keep the sealing surface smooth, and is suitable for harsh environments such as high temperature, dust and shaking on the continuous casting site, thereby improving the service life and operational stability of the equipment. 3. Precise Argon Gas Control for Better Protection: By monitoring argon gas parameters in real time through an argon gas flow back pressure gauge, the argon gas supply can be precisely controlled to ensure that the sealed area is under a slight positive pressure of argon gas throughout the process, completely avoiding contact between air and molten steel, effectively reducing the formation of Al2O3 inclusions, and improving the purity of molten steel and the quality of the billet. 4. Simple structure, convenient operation, and strong practicality: The device is composed of simple components such as long nozzle, high temperature fiber flat pad, and high temperature fiber cup pad. It does not require a complex power unit, is easy to install and replace, has low maintenance costs, and can be directly adapted to existing continuous casting production equipment, making it easy to promote and apply on a large scale in industry. 5. Strong adaptability and high stability: It can adapt to the positional displacement caused by the shaking of the ladle turntable when changing the ladle seat, avoid the sealing gap from becoming larger, ensure the sealing effect is stable, ensure the smooth operation of continuous casting production, reduce production costs, and help enterprises improve their high-end steel production capacity and product competitiveness. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the intermediate package structure of the present invention; In the diagram: 1. Ladle; 2. Ladle slide plate; 3. High-temperature fiber bowl pad; 4. Long water inlet; 5. High-temperature fiber flat pad; 6. Ladle drain outlet; 7. Long water inlet bowl inner cavity groove; 8. Flow and back pressure gauge; 9. Platform; 10. Argon gas pipeline. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] See attached document Figure 1 A combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle, comprising a ladle 1, a ladle slide plate 2, a long nozzle 4, and a ladle outlet 6, characterized in that: the inner cavity of the long nozzle 4 includes a bowl-shaped inner cavity and a cylindrical inner cavity, with a stepped platform 9 formed between the bowl-shaped inner cavity and the cylindrical inner cavity, and a high-temperature fiber flat pad 5 that cooperates with the ladle outlet 6 on the stepped platform 9; the bowl-shaped inner cavity is provided with a high-temperature fiber bowl pad 3 that cooperates with the ladle outlet 6 and an argon gas pipeline 10 that enters the bowl-shaped inner cavity.

[0020] In this embodiment, refer to the appendix Figure 1 This modular structure mainly includes a specially designed long water inlet 4, a high-temperature fiber flat gasket 5, a high-temperature fiber cup gasket 3, and a steel ladle drain outlet 6. These four components work together to achieve double sealing and argon gas protection. (1) The bottom of the inner cavity of the 4 bowl of the long water outlet is designed as a stepped structure. The stepped platform 9 is 1.5-2cm wide. The stepped platform 9 achieves surface-to-surface contact with the steel ladle water outlet 9. Compared with the traditional conical contact, it greatly improves the stability and tightness of the connection between the two and reduces the contact gap. (2) On the inner wall of the long water inlet 4 bowl, between 3-5cm from the bottom of the step platform 9 and 3-5cm below the top of the long water inlet 4 bowl, there is an annular groove 7 with an downward tilt angle of 12-18°. The downward opening of the groove can effectively prevent impurities in the argon gas and steel slag generated during the bag changing process from falling into the argon gas channel, preventing the channel from being blocked and ensuring smooth argon gas delivery. (3) The annular groove 7 is connected to the argon pipeline 10, and an argon flow back pressure gauge 8 is installed between the argon valve and the argon connection port of the long water nozzle bowl. It is used to monitor the argon flow and back pressure value in real time, so as to accurately control the argon supply parameters, maintain the argon micro-positive pressure in the sealed area, and ensure that the back pressure is ≥0.3 bar (30 kPa) to avoid argon leakage or excessive flow leading to slag entrainment in molten steel. (4) The inner cavity depth of the long water outlet 4 bowl is 10-12cm, and the inner cavity depth of the long water outlet 4 bowl is 0.5-2cm greater than the distance between the end of the large bag water outlet 6 and the steel ladle slide plate 2. This ensures that the steel ladle water outlet can be smoothly inserted into the long water outlet bowl, and when the long water outlet is connected to the large bag water outlet, the large bag slide plate squeezes the edge of the high temperature fiber bowl pad to achieve a seal between the large bag water outlet and the inner cavity of the long water outlet bowl and the outside world. At the same time, it can adapt to the positional shift of the long water outlet bowl and the large bag water outlet caused by the shaking of the steel ladle turntable when changing the bag seat, and avoid seal failure. (5) The high-temperature fiber bowl pad 3 is a conical barrel structure with a height of 3-5cm and a bowl with a rim of 3-5cm. The thickness of the conical barrel is 5-10mm and the thickness of the bowl rim is 10-15mm. The material can be selected according to the high-temperature conditions of continuous casting, such as high-alumina ceramic fiber, alumina fiber or aluminum silicate fiber. The high temperature resistance is ≥1750℃. The thickness of the high-temperature fiber flat pad 5 is 1-1.5cm. The material is matched with the high-temperature fiber bowl pad. It is mainly used to achieve the compression seal between the outlet plane of the ladle and the inner cavity step platform of the long nozzle bowl, forming the first sealing line, and at the same time preventing slag from sticking to the area above the inner cavity platform of the long nozzle bowl. (6) The high-temperature fiber flat gasket 5 squeezes the stepped platform of the long nozzle through the large package outlet, which plays the first sealing role and keeps the inner wall smooth. If the long nozzle bowl platform has slag, resulting in poor sealing of the high-temperature fiber flat gasket, the high-temperature fiber bowl gasket can achieve complete sealing between the long nozzle bowl and the outside world. The back pressure is monitored by the argon flow back pressure gauge to ensure that the back pressure is positive, and the inner cavity of the long nozzle bowl is in a state of complete argon protection, forming a double sealing protection. (7) During the control process, the argon flow rate is dynamically adjusted according to the steel pouring volume, steel characteristics and molten steel flow rate in the ladle to ensure the stability of the argon slightly positive pressure in the sealed area. When changing the ladle seat, the argon flow rate is increased in advance to avoid air intrusion. During the casting process, the sealing status and argon channel are checked regularly, and slag is cleaned in time to ensure the continuous and stable sealing effect. Example 1

[0021] This embodiment is applied to a 250-ton converter-continuous casting production line in a steel plant, which mainly produces aluminum deoxidized ultra-low carbon steel (steel grade DC06). This steel grade is used for high-end automotive stamping parts and has extremely high requirements for the purity of the molten steel. The oxygen content in the steel needs to be controlled within 25ppm. The traditional long nozzle sealing method has problems such as poor sealing, argon leakage, and slag adhesion in the bowl, resulting in a high surface defect rate of about 7.9% for the cast billet. The combined device and control method of this invention need to be used for improvement.

[0022] The specific implementation steps are as follows: (1) Structural configuration: A specially designed long nozzle 4 is selected, with a stepped structure at the bottom of its bowl cavity. The width of the stepped platform 9 is 1.5cm. The depth of the bowl cavity of the long nozzle 4 is designed to be 10cm. The distance between the end of the ladle outlet 6 and the ladle slide plate 2 is 9.2cm, ensuring that the depth of the bowl cavity of the long nozzle 4 is greater than this distance by more than 0.5cm. On the inner wall of the bowl cavity of the long nozzle 4, 3cm from the bottom of the stepped platform and 3cm from the top of the bowl, an annular groove 7 with an opening angle of 12° is opened. The cross-section of the annular groove 7 is rectangular, with a width of 5mm and a depth of 4mm. The annular groove 7 is connected to the argon supply system through an argon pipeline. An argon flow back pressure gauge 8 is installed between the argon valve and the argon connection port of the bowl cavity of the long nozzle 4. The range is 0-100kPa and the accuracy is ±0.5kPa, ensuring that the back pressure is ≥30kPa, which is suitable for the purity requirements of DC06 steel.

[0023] The system is equipped with a high-temperature fiber flat pad 5 and a high-temperature fiber bowl pad 3. The high-temperature fiber flat pad 5 is made of alumina fiber with a thickness of 1.0cm and a diameter of 13cm, which is the same as the diameter of the stepped platform inside the bowl of the long water inlet 4. The high-temperature fiber bowl pad 3 has a conical barrel structure with a height of 3.0cm, a bowl rim width of 3.0cm, a conical barrel thickness of 5mm, and a bowl rim thickness of 10mm. It is made of high-alumina ceramic fiber, with a high temperature resistance of ≥1780℃ and good elasticity and high-temperature wear resistance.

[0024] (2) Structural assembly: First, lay the high-temperature fiber flat pad 5 flat on the stepped platform 9 of the inner cavity of the long nozzle 4 bowl, ensuring that the flat pad is laid flat, without wrinkles or deviation; then, put the high-temperature fiber bowl pad 3 on the end of the 250-ton ladle outlet 6, so that the conical barrel of the bowl pad fits tightly against the outer wall of the ladle outlet 6, with the bowl edge facing upward; finally, move the ladle 1 to the top of the continuous casting tundish through the ladle turntable, slowly lower the ladle 1, so that the ladle outlet 6 is smoothly inserted into the inner cavity of the long nozzle 4 bowl, until the ladle slide plate 2 and the bowl edge of the high-temperature fiber bowl pad 3 are tightly squeezed (the squeezing amount is 1.5-2mm). At this time, under the squeezing action of the ladle outlet 6, the high-temperature fiber flat pad 5 forms a tight seal with the stepped platform of the long nozzle 4 without gaps.

[0025] (3) Control method: Start the argon supply system, open the argon valve, and monitor the argon flow rate and back pressure value in real time through the argon flow rate and back pressure gauge 8. Initially adjust the argon flow rate to 15L / min (suitable for the casting flow rate of DC06 steel grade in a 250-ton converter), and maintain the back pressure value at 30-36kPa (meeting the requirement of ≥0.3bar). During the continuous casting process, observe the changes in the value of the argon flow rate and back pressure gauge 8 in real time. If the back pressure value is lower than 30kPa, it indicates that there is argon leakage or channel blockage. Increase the argon flow rate to 18-20 L / min, and at the same time check the sealing status of the high-temperature fiber flat gasket 5 and the high-temperature fiber cup gasket 3. If slag is found, clean it in time with a special high-temperature resistant tool. If the back pressure value is higher than 36 kPa, reduce the argon flow rate appropriately to avoid the molten steel from being slag-coiled due to excessive argon flow rate. When changing the ladle seat, increase the argon flow rate to 20 L / min in advance. After the ladle drain port 6 is inserted in place and the seal is stable, adjust the argon flow rate back to 15 L / min to avoid air intrusion during the ladle change process.

[0026] (4) Implementation effect: After adopting the present invention, the argon leakage rate was reduced to below 0.4L / min, and the back pressure was stabilized and maintained at a slightly positive pressure; the slag adhesion rate in the bowl was reduced from 58% to below 4%, and the argon channel was unblocked; the oxygen content of DC06 molten steel was stabilized at 22-24ppm, and the surface defect rate of the billet was reduced to 1.5%; maintenance costs were reduced by 32%, and the continuous casting production smoothness rate was increased to 99.6%. Example 2

[0027] This embodiment is applied to a 250-ton converter-continuous casting production line in a steel plant to produce aluminum-deoxidized high-strength duplex steel (grade 980DP). This steel is used for structural components such as automotive anti-collision beams and vehicle frames. It requires an oxygen content of ≤35ppm and no oxidation inclusions or defects inside the billet. Traditional sealing methods suffer from poor sealing stability due to the shaking of the ladle tumbler, resulting in serious argon leakage, secondary oxidation of the molten steel, and a high defect rate inside the billet (approximately 6.8%). Therefore, the technology of this invention is needed for improvement.

[0028] The specific implementation steps are as follows: (1) Structural configuration: The bottom of the inner cavity of the long water inlet 4 bowl is a stepped structure, and the width of the stepped platform 9 is 1.75cm; the inner cavity of the long water inlet 4 bowl is designed to be 11cm deep, and the distance between the end of the large water outlet 6 and the steel ladle slide plate 2 is 9.8cm, ensuring that the inner cavity depth of the long water inlet 4 bowl is greater than this distance by 1.25cm; on the inner cavity wall of the long water inlet 4 bowl, 4cm from the bottom of the stepped platform and 4cm below the top of the bowl, an annular groove 7 with an opening angle of 15° is opened downward. The cross section of the annular groove 7 is semi-circular and the diameter is 7mm; the annular groove 7 is connected to the argon gas pipeline, and the argon gas flow back pressure gauge 8 has a range of 0-100kPa and an accuracy of ±0.5kPa, ensuring that the back pressure is ≥30kPa.

[0029] The high-temperature fiber flat pad 5 is made of aluminum silicate fiber with a thickness of 1.25cm and a diameter of 14.5cm to match the stepped platform, which is the size of the drain outlet of the steel ladle. The high-temperature fiber bowl pad 3 has a conical barrel structure with a height of 4cm, a bowl rim width of 4cm, a conical barrel thickness of 7.5mm, a bowl rim thickness of 12.5mm, a high temperature resistance of ≥1800℃, and good sealing elasticity and wear resistance.

[0030] (2) Structural assembly: First, lay the high-temperature fiber flat pad 5 flat on the stepped platform of the inner cavity of the long nozzle 4 bowl, and fix it with high-temperature resistant adhesive to ensure that the flat pad is laid flat, without wrinkles, and without deviation; then, put the high-temperature fiber bowl pad 3 on the end of the ladle outlet 6, adjust the position so that the conical barrel of the bowl pad fits tightly with the outer wall of the ladle outlet 6, with the bowl edge facing upward and horizontal; finally, move the ladle 1 precisely to the top of the continuous casting tundish through the ladle turntable, and slowly lower the ladle 1 so that the ladle outlet 6 is smoothly inserted into the inner cavity of the long nozzle 4 bowl until the ladle slide plate 2 and the bowl edge of the high-temperature fiber bowl pad 3 are tightly squeezed (the squeezing amount is 2-2.5mm). At this time, the high-temperature fiber flat pad 5 undergoes slight deformation under the squeezing action of the ladle outlet 6, forming a seamless seal with the stepped platform of the long nozzle 4.

[0031] (3) Control method: Start the argon supply system and adjust the argon flow rate to 16L / min. Maintain the back pressure value at 30-40kPa through the argon flow rate back pressure gauge 8. During the steel pouring process, check the back pressure value and sealing status every 25 minutes. Monitor the linkage change between the molten steel flow rate and the back pressure value in real time. When the molten steel flow rate increases to ≥2.8m / s, appropriately increase the argon flow rate to 19-21L / min to ensure stable back pressure. If the back pressure value drops due to the shaking of the ladle turntable, adjust the argon flow rate in time to avoid sealing failure. When changing the ladle seat, increase the argon flow rate to 21L / min in advance. After the ladle drain outlet 6 is inserted into place and the seal is stable, gradually adjust the argon flow rate back to 16L / min to prevent air intrusion during the ladle change process and avoid secondary oxidation of 980DP molten steel.

[0032] (4) Implementation results: the seat shakes without sealing failure, the argon gas micro-positive pressure is stable and controllable; the oxygen content of 980DP molten steel is stable at 32-34ppm, the internal oxidation inclusion defect rate of the billet is reduced from 6.8% to 1.4%; the frequency of cleaning slag adhering to the bowl is reduced by 75%, the production cost is significantly reduced, and the high-end quality requirements of automotive structural parts are met. Example 3

[0033] This embodiment is applied to a 250-ton converter-continuous casting production line in a steel plant to achieve an oxygen content of ≤25ppm in DC04 ultra-low carbon steel. Traditional sealing methods suffer from serious argon leakage, poor sealing stability, and easy slag adhesion in the bowl, resulting in substandard steel purity and a high internal defect rate (approximately 5.9%) in the cast billet. Therefore, the combined device and control method of this invention need to be used for improvement.

[0034] The specific implementation steps are as follows: (1) Structural configuration: The bottom of the inner cavity of the long water inlet 4 bowl is a stepped structure, and the width of the stepped platform 9 is 2cm; the inner cavity of the long water inlet 4 bowl is designed to be 12cm deep, and the distance between the end of the ladle water outlet 6 and the ladle slide plate 2 is 10.2cm, ensuring that the inner cavity depth of the long water inlet 4 bowl is greater than this distance by 2.0cm; on the inner wall of the long water inlet 4 bowl, 5cm from the bottom of the stepped platform and 5cm below the top of the bowl, an annular groove 7 with an opening angle of 17° is opened. The cross section of the annular groove 7 is semi-circular and the diameter is 9mm; the annular groove 7 is connected to the argon supply system through an argon pipeline. An argon flow back pressure gauge 8 is installed between the argon valve and the argon connection port of the long water inlet 4 bowl, with a range of 0-100kPa and an accuracy of ±0.5kPa, ensuring that the back pressure is ≥30kPa, which is suitable for the needs of alternating production of two steel grades.

[0035] The high-temperature fiber flat pad 5 is made of high-purity ceramic fiber material, with a thickness of 1.5cm and a diameter of 15.5cm to match the stepped platform; the high-temperature fiber bowl pad 3 has a conical barrel structure with a height of 5cm, a bowl rim width of 5cm, a conical barrel thickness of 10mm, a bowl rim thickness of 15mm, a high temperature resistance of ≥1850℃, and excellent high temperature resistance, wear resistance, and sealing elasticity.

[0036] (2) Structural assembly: First, lay the high-temperature fiber flat pad 5 flat on the stepped platform of the inner cavity of the long nozzle 4 bowl, and fix it with high-temperature resistant adhesive to ensure that the flat pad is laid flat, without wrinkles, and without deviation; then, put the high-temperature fiber bowl pad 3 on the end of the ladle drain 6, adjust the position so that the conical barrel of the bowl pad fits tightly with the outer wall of the ladle drain 6, with the bowl edge facing upward and horizontal; finally, move the ladle 1 precisely to the top of the continuous casting tundish through the ladle turntable, and slowly lower the ladle 1 so that the ladle drain 6 is smoothly inserted into the inner cavity of the long nozzle 4 bowl until the ladle slide plate 2 and the bowl edge of the high-temperature fiber bowl pad 3 are tightly squeezed (the squeezing amount is 2.5-3mm). At this time, the high-temperature fiber flat pad 5 undergoes slight deformation under the squeezing action of the ladle drain 6, forming a seamless seal with the stepped platform of the long nozzle 4 to ensure no argon leakage.

[0037] (3) Control method: Start the argon supply system, open the argon valve, and dynamically adjust the argon flow rate according to the steel grade to be cast. When casting DC04 steel, the initial argon flow rate is adjusted to 15L / min, and the back pressure value is maintained at 30-36kPa. During the steel casting process, monitor the linkage change between the molten steel flow rate and the back pressure value in real time. When the molten steel flow rate increases (≥3.0m / s), the argon flow rate is appropriately increased by 2-3L / min to ensure the back pressure is stable. Check the sealing status and argon channel every 18 minutes. If a small amount of slag is found in the bowl of the long nozzle, clean it with special tools in time to avoid affecting the sealing effect. When changing the ladle and switching the steel grade, increase the argon flow rate to 22L / min in advance. After the ladle outlet 6 is inserted into place and the seal is stable, gradually adjust the argon flow rate to the initial value of the corresponding steel grade to prevent air intrusion during the ladle change and steel grade switching process and ensure the purity of the two types of molten steel.

[0038] (4) Implementation results: Argon leakage was reduced to below 0.25 L / min, and the micro-positive pressure remained stable; the slag adhesion rate in the bowl was reduced from 52% to below 2.5%, and there was no blockage in the argon channel; the oxygen content of DC04 molten steel was stabilized at 22-24 ppm, and the internal defect rate of the billet was reduced to 1.2%; the service life of the equipment reached 9.5 heats / unit, the maintenance cost was reduced by 35%, and the continuous casting smoothness rate was increased to 99.8%.

Claims

1. A combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle, comprising a ladle (1), a ladle slide plate (2), a long nozzle (4), and a ladle outlet (6), characterized in that: The inner cavity of the long water outlet (4) includes a bowl-shaped inner cavity and a cylindrical inner cavity. The bowl-shaped inner cavity and the cylindrical inner cavity form a stepped platform (9). A high-temperature fiber flat pad (5) that matches the ladle water outlet (6) is provided on the stepped platform (9). A high-temperature fiber bowl pad (3) that matches the ladle water outlet (6) and an argon gas pipeline (10) that enters the bowl-shaped inner cavity are provided.

2. The combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle according to claim 1, characterized in that: The bowl-shaped inner cavity of the long water inlet (4) is provided with a groove (7) in the circumferential direction that is connected to the argon pipeline (10), and a flow back pressure gauge (8) is installed on the argon pipeline (10).

3. The combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle according to claim 2, characterized in that: The groove (7) inside the long water inlet bowl is a downward-sloping annular groove.

4. The combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle according to claim 3, characterized in that: The downward inclination angle of the groove (7) inside the long water spout bowl is 12-18°.

5. The combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle according to claim 1, characterized in that: The width of the stepped platform (9) formed between the inner cavity of the bowl and the inner cavity of the column is 1.5-2cm.

6. The combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle according to claim 1, characterized in that: The depth of the inner cavity of the bowl of the long water outlet (4) is 0.5-2cm greater than the distance between the end of the ladle water outlet (6) and the steel plate slide plate (2).

7. The combined structure for improving the sealing performance of the bowl section of a continuous casting nozzle according to claim 1, characterized in that: The high-temperature fiber bowl pad (3) is provided with a bowl edge that matches the steel ladle slide plate (2).

8. A method for improving the sealing performance of the bowl section of a continuous casting nozzle, characterized in that: The combined structure for improving the sealing of the bowl of the long nozzle in continuous casting is adopted as defined in any one of claims 1-7. During the casting process, the argon flow rate is dynamically adjusted according to the steel pouring volume, steel characteristics and molten steel flow rate in the ladle to ensure that the argon in the inner cavity of the bowl of the long nozzle (4) is in a slightly positive pressure state.

9. The method for controlling the sealing performance of the bowl section of a continuous casting nozzle according to claim 8, characterized in that: During the casting process, the high-temperature fiber flat pad (5) squeezes the stepped platform (9) of the bowl cavity of the long nozzle (4) through the ladle drain (6), which plays a sealing role and keeps the inner wall of the bowl cavity smooth; at the same time, argon gas is introduced into the bowl cavity of the long nozzle (4) to ensure that the bowl cavity of the long nozzle (4) is in a state of complete argon gas protection.

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