Optimized process for RH vacuum refining of high-purity special steel

Abstract

The application relates to the technical field of steel production, and discloses a high-purity special steel RH vacuum refining optimization process, which comprises the following steps: S1, pretreatment and multi-parameter online detection deployment; S2, staged gradient type vacuum-lifting gas synergic regulation and control; S3, precise pulse injection based on a real-time flow field; and S4, purity dynamic control and tapping. The high-purity special steel RH vacuum refining optimization process is linked through multi-parameter online detection and staged gradient regulation, a precise and stable molten steel flow field is constructed, the inherent contradiction between decarburization and inclusion removal in the traditional process is solved, different sizes, modification and spheroidization are realized, and the functional limitation of a single refining mode is broken through; the dynamic anti-nodular coating is matched with the directional flow guide structure, the process stability is ensured, the inclusion floating efficiency is strengthened, a whole-process closed-loop control system is formed, the molten steel purity and process adaptability are simultaneously broken through, and the strict requirement of high-end special steel on inclusion control is met.

Description

Technical Field

[0001] This invention relates to the field of steel production technology, specifically to an optimized process for high-purity special steel RH vacuum refining. Background Technology

[0002] RH vacuum refining is a core refining process in the production of high-end special steels. It plays a crucial role in decarburization, degassing, inclusion removal, and precise composition control, directly determining the mechanical properties and service life of the final steel. With the rapid development of high-end equipment manufacturing industries such as aerospace, wind power, and rail transportation, more stringent requirements have been placed on the purity of special steels, especially the control of the quantity, size, and morphology of inclusions, driving the RH refining process to continuously upgrade towards refinement and intelligence.

[0003] Current RH refining processes generally employ relatively fixed vacuum levels and gas flow control modes, making it difficult to simultaneously meet the dual requirements of rapid decarburization and inclusion removal. The intense circulation during the strong decarburization stage easily leads to slag entrapment and secondary oxidation, while the later gentle circulation is insufficient to effectively remove fine inclusions. Existing refining processes often use a single-component refining agent added all at once and single-size bubble blowing, lacking the ability to specifically treat inclusions of different sizes and types. This results in low refining agent utilization and limited modification effects on hard inclusions. Furthermore, existing impregnation tube coatings have limited functionality, making it difficult to effectively control nodule formation, easily leading to distortion of the molten steel flow field, insufficient process stability, and the formation of circulation dead zones at the bottom of the vacuum chamber, causing inclusion deposition and retention. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an optimized process for high-purity special steel RH vacuum refining, which solves the technical problems of existing RH refining processes that are unable to simultaneously meet the dual requirements of rapid decarburization and inclusion removal, lack of targeted treatment capabilities for inclusions by single-component refining agents and single-size bubbles, single-function coating of impregnation tubes that is prone to nodule formation, and inclusion deposition and retention caused by circulation dead zones at the bottom of the vacuum chamber.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an optimized process for high-purity special steel RH vacuum refining, comprising: S1. Preprocessing and multi-parameter online detection deployment: A laser-induced breakdown spectroscopy online composition analyzer is installed at the top of the RH vacuum chamber to achieve millisecond-level real-time detection of key components such as carbon and oxygen in molten steel. This avoids the lag of traditional offline sampling and analysis, providing core data support for subsequent staged precise control. Temperature sensors and electromagnetic flowmeters are installed at the inlet of the riser pipe and the outlet of the downcomer pipe, respectively, to monitor the molten steel circulation status in real time, accurately calculate the actual circulation flow rate and temperature field distribution, and eliminate flow field deviations caused by tube nodules or fluctuations in operating conditions. An online inclusion monitor is installed on the side wall of the vacuum chamber to achieve continuous online monitoring of the quantity, size, and morphology of inclusions without interrupting the process sampling, providing real-time basis for dynamic adjustments in the purity control stage. The riser pipe is set so that the lower diameter is 15%-20% larger than the upper diameter. The variable diameter structure allows the molten steel flow velocity in the riser to gradually increase along the axial direction, reducing eddies and dead zones during the steel's ascent, improving steel circulation efficiency, and reducing local scouring and erosion of the inner wall of the immersion tube. Eccentric auxiliary gas nozzles with axes offset from the center of the riser are evenly arranged around the inner circumference of the riser, forming a spiraling axial swirling flow field within the riser, enhancing the mixing effect of the molten steel, making the composition and temperature more uniform, and promoting full contact between bubbles and molten steel. An online-activated dynamic anti-nodulation composite coating is applied to the inner wall of the immersion tube, solving the industry pain points of severe nodulation and short service life in traditional immersion tubes, ensuring the stability and consistency of the molten steel flow field throughout the entire process. An arc-shaped directional flow guide structure matching the direction of molten steel circulation is installed at the bottom of the vacuum chamber, breaking the dead zone at the bottom of the vacuum chamber, preventing long-term deposition of inclusions, and providing a guiding basis for the directional flotation of subsequent inclusions. S2. Staged gradient vacuum-lift gas coordinated control: The RH treatment process is divided into three continuous stages: rapid decarburization, transition, and purity control. The transition stage begins when the carbon content of the molten steel drops to 0.03%–0.05%, and the purity control stage begins when the carbon content drops below 0.005%. This breaks with traditional RH treatment methods. The crude control mode of single vacuum degree and boost gas flow fundamentally solves the inherent contradiction between rapid decarburization and inclusion removal, and achieves simultaneous improvement of decarburization efficiency and steel purity. Based on real-time data of steel carbon content, oxygen content and temperature, the vacuum degree and boost gas flow are dynamically adjusted to achieve precise matching of process parameters with the actual state of the steel, avoiding process fluctuations caused by fixed parameters. In the rapid decarburization stage, the vacuum degree is rapidly reduced to 67-133 Pa and the eccentric auxiliary gas nozzle is opened to form an axial swirling flow field. At the same time, the high temperature of the steel itself activates the high temperature resistance and anti-oxidation function of the coating. In the transition stage, the vacuum degree is gradually increased to 200-300 Pa and the boost gas flow is reduced. By spraying a small amount of air into the immersion tube, the self-cleaning function of the coating is activated. In the purity control stage, the vacuum degree is maintained at 400-500 Pa and a gentle and stable steel circulation is maintained, providing sufficient time and stable kinetic conditions for the flotation and removal of inclusions, avoiding inclusion breakage and secondary entrainment caused by strong circulation. S3. Precise pulse injection based on real-time flow field: The uniform and stable molten steel flow field constructed through the S2 staged gradient vacuum-lifting gas synergistic control is the core foundation of the two improvements in this invention. This provides the prerequisite for the uniform distribution and directional movement of the refining agent and microbubbles. Combined with real-time collected velocity and flow rate data, when the molten steel velocity is 0.8–1.2 m / s and the turbulence intensity is 5%–10%, the lower part of the riser pipe and the bottom circulation zone of the vacuum chamber are identified as the two optimal injection points. The molten steel velocity and turbulence intensity at these two locations are precisely designed to ensure sufficient dispersion of the refining agent and microbubbles without aggregation, maximizing the contact probability between the refining agent and inclusions. At the end of the transition stage, the refining agent and microbubbles are injected alternately in a pulsed manner, first through the injection point in the lower part of the riser pipe and then through the injection point in the bottom circulation zone of the vacuum chamber. The first-stage microbubbles have a diameter of 50–100 μm. The second-stage microbubbles, with a diameter of 100-200 μm, achieve precise matching between the refining agent, microbubbles, and the flow field of molten steel. This avoids the problems of localized refining agent aggregation and excessively rapid microbubble rise in traditional processes, significantly improving the utilization rate of the refining agent and the efficiency of inclusion removal. First, a first-gradient pre-melted slag refining agent is injected to adsorb large inclusions with the first-stage microbubbles. The first-gradient pre-melted slag refining agent has good fluidity and adsorption capacity, enabling it to quickly adsorb large inclusions in the molten steel. The first-stage microbubbles then capture inclusions <10 μm through collision and adhesion. The process involves two steps: first, the separation of inclusions of different sizes is achieved through the synergistic effect of ultrafine inclusions and the addition of a second-stage refining agent containing rare earth elements and a second-stage microbubble modification to capture fine inclusions. Rare earth elements Ce and La can react with hard Al2O3 inclusions, modifying them into low-melting-point, easily floating rare earth aluminate inclusions. The second-stage microbubbles specifically capture the modified 10-20μm fine inclusions, further improving the inclusion removal rate. Finally, a third-stage refining agent containing MgO is injected to refine and spherize the inclusions. MgO can refine the inclusion size, while CaSi can further reduce the melting point of the inclusions, promote spheroidization, and improve the fatigue life and impact resistance of the molten steel. S4. Dynamic control of purity and steel tapping: During the purity control stage, the amount of refining agent injected and the pulse interval time are dynamically adjusted based on online monitoring data of inclusions. When the number of inclusions <20μm exceeds 10 / mm², the amount of refining agent injected is increased by 10%-15% and the pulse interval is shortened by 5 seconds to achieve closed-loop control of the inclusion removal process, avoiding over-refining or under-refining, and ensuring the stability and consistency of the purity of molten steel in different heats. A directional flow guide structure at the bottom of the vacuum chamber is used to construct a directional floating channel for inclusions, guiding microbubbles carrying inclusions to the slag layer area at the top of the vacuum chamber, accelerating the floating speed of inclusions, and preventing inclusions from being retained or secondary entrained in the molten steel. Purity is considered met when the total oxygen content of the molten steel is ≤5ppm, the removal rate of <10μm ultrafine inclusions is ≥75%, and the removal rate of <20μm fine inclusions is ≥90%. After 5-10 days of monitoring... After a few minutes of pure circulation processing, the steel is unloaded from the vacuum, further homogenizing the composition and temperature of the molten steel. This allows any remaining fine inclusions to float to the surface, ensuring that the purity of the molten steel before tapping meets the requirements for high-end special steel.

[0006] Preferably, in the S2 stage of phased gradient vacuum-lift gas coordinated control, the vacuum degree of the rapid decarburization stage is 67-133 Pa, and the lift gas flow rate is 120-150 Nm³ / h; the vacuum degree of the transition stage is 200-300 Pa, and the lift gas flow rate is 80-100 Nm³ / h; and the vacuum degree of the purity control stage is 400-500 Pa, and the lift gas flow rate is 50-70 Nm³ / h. This parameter range has been optimized and determined through a large number of industrial tests, which can minimize secondary oxidation and slag entrainment while ensuring decarburization efficiency, and create good thermodynamic and kinetic conditions for inclusion removal.

[0007] Preferably, in the S1, pretreatment and multi-parameter online detection deployment, the number of eccentric auxiliary gas nozzles is 4-6, the nozzle axis forms an angle of 15-30° with the tangent direction of the inner wall of the riser, and the auxiliary gas flow rate is 10-15% of the main booster gas flow rate. This structural parameter can form a stable and moderately strong swirling field in the riser, which not only ensures the stirring and mixing effect of molten steel, but also prevents molten steel from splashing and secondary oxidation due to excessive swirling intensity.

[0008] Preferably, the dynamic anti-nodulation composite coating in S1, pretreatment and multi-parameter online detection deployment is composed of a MgO-Cr2O3-ZrO2 ternary matrix and an active functional layer doped with TiO2 and CeO2. During the rapid decarburization stage, the high temperature of the molten steel activates the high-temperature resistance and anti-oxidation function, and during the transition stage, the self-cleaning function is activated by injecting a small amount of air at a flow rate of 5-10 Nm³ / h. The MgO-Cr2O3-ZrO2 ternary matrix has excellent high-temperature resistance and anti-corrosion properties, and the doped TiO2 and CeO2 active components can be selectively activated under different conditions to achieve high-temperature resistance, anti-oxidation and self-cleaning functions, respectively, thus extending the service life of the impregnated tube by 30%-40%.

[0009] Preferably, in S3, the mass ratio of the three batches of the gradient component composite refining agent in the precise pulse injection based on the real-time flow field is as follows: the first gradient is a CaO-CaF2-Al2O3 pre-melted slag with a mass ratio of 7:2:1; the second gradient is a pre-melted slag with 5%-8% Ce and 2%-3% La added to the first gradient; and the third gradient is a pre-melted slag with 3%-5% MgO and 1%-2% CaSi added to the second gradient. The gradient component design can target the refining agent according to the type and size of inclusions at different stages, avoid the single-function defect of single-component refining agents, and significantly improve the overall refining effect of the refining agent.

[0010] Preferably, in step S3, the graded particle size argon microbubbles in the precise pulse injection based on the real-time flow field are divided into two stages. The first stage has a diameter of 50-100μm and is used to capture ultrafine inclusions <10μm. The second stage has a diameter of 100-200μm and is used to capture fine inclusions 10-20μm. The volume ratio of the two stages of microbubbles is 1:1. The graded particle size design can achieve precise capture of inclusions of different sizes, solving the industry problem of low capture efficiency of ultrafine inclusions by traditional single-size microbubbles, and greatly improving the removal rate of fine inclusions <20μm.

[0011] Preferably, in S3, the pulsed alternating injection sequence based on real-time flow field precision pulse injection is as follows: after injecting the refining agent for 5-10 seconds, there is an interval of 10-15 seconds, followed by the injection of microbubbles for 10-15 seconds. The total amount of refining agent injected is 1.5-2.5 kg / t steel, and the total amount of microbubbles injected is 0.3-0.5 Nm³ / t steel. This injection sequence enables the refining agent and microbubbles to form a continuous process of "adsorption-modification-capture-floatation" in the molten steel, avoiding mutual interference caused by the simultaneous injection of refining agent and microbubbles. The total injection amount is optimized, which can reduce the consumption of refining agent and production costs while ensuring the refining effect.

[0012] Preferably, the directional flow guidance structure described in S1, pretreatment and multi-parameter online detection deployment consists of 4-6 arc-shaped flow guide plates. The flow guide plates form an angle of 30-45° with the bottom of the vacuum chamber, and the height is 1 / 8-1 / 6 of the height of the vacuum chamber. The radius of curvature is consistent with the bottom of the vacuum chamber. These structural parameters can perfectly match the direction of the molten steel circulation constructed in S2, forming an efficient directional floating channel for inclusions, increasing the floating speed of inclusions by more than 40%, and effectively eliminating the circulation dead zone at the bottom of the vacuum chamber.

[0013] Preferably, in the rapid decarburization stage of the phased gradient vacuum-lift gas coordinated control in S2, when the initial oxygen content of the molten steel is <500ppm, oxygen is injected through the oxygen lance at the top of the vacuum chamber at a flow rate of 50-80Nm³ / h for 2-3 minutes. This can accurately replenish the oxygen potential required for the decarburization reaction, avoid the decrease in decarburization rate and incomplete decarburization caused by insufficient oxygen content, and ensure the treatment effect of the rapid decarburization stage.

[0014] Preferably, in S4, the dynamic control of purity and the tapping of steel, the total oxygen content of the treated molten steel is ≤5ppm, the removal rate of <10μm ultrafine inclusions is ≥75%, the removal rate of <20μm fine inclusions is ≥90%, the inclusion spheroidization rate is ≥95%, and the total recovery rate of rare earth elements is ≥75%. These indicators are far superior to the traditional RH refining process, which can meet the stringent requirements of high-end fields such as aerospace, wind power, and rail transportation for the purity of special steel, and significantly improve the fatigue life and impact resistance of special steel.

[0015] Compared with existing technologies, this invention provides an optimized process for high-purity special steel RH vacuum refining, which has the following beneficial effects: This optimized RH vacuum refining process for high-purity special steel, through the linkage of multi-parameter online detection and staged gradient control, constructs a precise and stable molten steel flow field, resolving the inherent contradiction between decarburization and inclusion removal in traditional processes. By leveraging the pulsed synergistic injection of gradient refining agents and graded microbubbles, it achieves the directional separation, modification, and spheroidization of inclusions of different sizes and types, overcoming the functional limitations of single refining methods. The combination of a dynamic anti-nodulation coating and a directional flow-guiding structure ensures process stability and enhances inclusion flotation efficiency, forming a closed-loop control system throughout the entire process. This achieves simultaneous breakthroughs in steel purity and process adaptability, meeting the stringent requirements of high-end special steel for inclusion control. Attached Figure Description

[0016] Figure 1 This is a system flowchart of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides a technical solution; please refer to [link / reference]. Figure 1 An optimized process for high-purity special steel RH vacuum refining includes: S1. Preprocessing and multi-parameter online detection deployment: A laser-induced breakdown spectroscopy online component analyzer is installed at the top of the RH vacuum chamber to achieve millisecond-level real-time detection of key components such as carbon and oxygen in molten steel. This avoids the lag of traditional offline sampling and analysis, providing core data support for subsequent staged precise control. Temperature sensors and electromagnetic flowmeters are installed at the inlet and outlet of the immersion tube to monitor the molten steel circulation status in real time, accurately calculate the actual circulation flow rate and temperature field distribution, and eliminate flow field deviations caused by immersion tube nodules or fluctuations in operating conditions. An online inclusion monitor is installed on the side wall of the vacuum chamber to achieve continuous online monitoring of the quantity, size, and morphology of inclusions without interrupting process sampling, providing real-time basis for dynamic adjustments in the purity control stage. The riser pipe is configured with a variable diameter structure where the lower diameter is 15%-20% larger than the upper diameter, allowing the molten steel flow velocity in the riser pipe to gradually increase along the axial direction. The process of raising the molten steel in the rising tube reduces eddies and dead zones during the steel's ascent, improving steel circulation efficiency and reducing local scouring and erosion of the inner wall of the immersion tube. Eccentric auxiliary gas nozzles are evenly arranged around the circumference of the inner wall of the rising tube to create a spiraling axial swirling flow field, enhancing the mixing effect of the molten steel and making the composition and temperature more uniform. This also promotes full contact between air bubbles and the molten steel. An online-activated dynamic anti-nodulation composite coating is applied to the inner wall of the immersion tube, addressing the industry pain points of severe nodulation and short service life in traditional immersion tubes, ensuring the stability and consistency of the steel flow field throughout the entire process. An arc-shaped directional flow guide structure matching the direction of the molten steel circulation is installed at the bottom of the vacuum chamber to disrupt the dead zone at the bottom of the vacuum chamber, preventing long-term deposition of inclusions and providing a guiding foundation for the directional flotation of subsequent inclusions.

[0019] S2. Staged gradient vacuum-lift gas coordinated control: The RH treatment process is divided into three consecutive stages: rapid decarburization, transition, and purity control. This breaks away from the traditional RH process's crude control mode of simply adjusting vacuum level and increasing gas flow rate. It fundamentally resolves the inherent contradiction between rapid decarburization and inclusion removal, achieving simultaneous improvement in decarburization efficiency and steel purity. Based on real-time data on the carbon content, oxygen content, and temperature of the molten steel, the vacuum level and gas flow rate are dynamically adjusted to achieve precise matching between process parameters and the actual state of the molten steel, avoiding process fluctuations caused by fixed parameters. In the rapid decarburization stage, the vacuum level is rapidly reduced, and the eccentric auxiliary gas nozzle is activated to form an axial swirling flow field, simultaneously activating the coating. Its high-temperature resistance and oxidation resistance significantly improve the decarburization reaction rate and shorten the decarburization time. At the same time, it prevents the corrosion of the inner wall of the immersion tube by high-temperature molten steel and slag, and extends the service life of the immersion tube. During the transition stage, the vacuum degree is gradually increased and the lifting gas flow rate is reduced to activate the self-cleaning function of the coating, avoid slag entrapment and secondary oxidation caused by strong circulation, reduce the generation of initial inclusions, and loosen and remove the formed nodule layer. It maintains the stability of the molten steel circulation flow rate. During the purity control stage, it maintains a mild and stable molten steel circulation, providing sufficient time and stable kinetic conditions for the flotation and removal of inclusions, and avoiding inclusion breakage and secondary entrainment caused by strong circulation.

[0020] S3. Precise pulse injection based on real-time flow field: The uniform and stable molten steel flow field constructed by utilizing S2 and staged gradient vacuum-lifting gas synergistic control is the core foundation of the linkage between the two improvement points of this invention. It provides the prerequisite for the uniform distribution and directional movement of refining agent and microbubbles. Combined with real-time collected flow velocity and flow rate data, two optimal injection points are dynamically determined: the lower part of the riser pipe and the bottom circulation zone of the vacuum chamber. The molten steel flow velocity and turbulence intensity at these two locations are just right to ensure that the refining agent and microbubbles are fully dispersed and do not aggregate, maximizing the contact probability between the refining agent and inclusions. At the end of the transition stage, gradient component composite refining agent and graded particle size argon microbubbles are injected alternately in a pulsed manner at the two injection points to achieve precise matching between the refining agent and microbubbles and the molten steel flow field. This avoids the problems of local aggregation of refining agent and excessively rapid floating of microbubbles in traditional processes, significantly improving the utilization rate of refining agent and the efficiency of inclusion removal. First, the first gradient pre-melted slag refining agent and the first stage are injected. Microbubble adsorption of large inclusions: The first-gradient pre-melted slag refining agent has good fluidity and adsorption capacity, enabling it to quickly adsorb large inclusions in molten steel. The first-stage microbubbles capture ultrafine inclusions through collision and adhesion. The two work together to achieve the initial separation of inclusions of different sizes. Then, a second-gradient refining agent containing rare earth elements is injected to modify and capture fine inclusions with the second-stage microbubbles. Rare earth elements Ce and La can react with hard Al2O3 inclusions, modifying them into low-melting-point, easily floating rare earth aluminate inclusions. The second-stage microbubbles specifically capture the modified 10-20μm fine inclusions, further improving the inclusion removal rate. Finally, a third-gradient refining agent containing MgO is injected to refine and spheroidize the inclusions. MgO can refine the size of the inclusions, and CaSi can further reduce the melting point of the inclusions, promote the spheroidization of the inclusions, and improve the fatigue life and impact resistance of the molten steel.

[0021] S4. Dynamic control of purity and steel tapping: During the purity control stage, pulse injection parameters are adjusted based on online inclusion monitoring data to achieve closed-loop control of the inclusion removal process. This avoids over-refining or under-refining, ensuring the stability and consistency of steel purity across different heats. A directional flow guide structure at the bottom of the vacuum chamber is used to construct a directional floating channel for inclusions, guiding microbubbles carrying inclusions to the slag layer at the top of the vacuum chamber. This accelerates the floating speed of inclusions, preventing their retention and secondary entrainment in the molten steel until the steel purity meets the standard. After pure circulation treatment, the vacuum is broken and the steel is tapped, further homogenizing the composition and temperature of the molten steel. This allows any remaining fine inclusions to float fully, ensuring that the purity of the molten steel before tapping meets the requirements for high-end special steel.

[0022] S2. In the phased gradient vacuum-lift gas synergistic control system, the rapid decarburization stage has a vacuum level of 67-133 Pa and a lift gas flow rate of 120-150 Nm³ / h. The transition stage has a vacuum level of 200-300 Pa and a lift gas flow rate of 80-100 Nm³ / h. The purity control stage has a vacuum level of 400-500 Pa and a lift gas flow rate of 50-70 Nm³ / h. These parameter ranges were determined through extensive industrial testing and optimization. This ensures decarburization efficiency while minimizing secondary oxidation and slag entrainment, creating favorable thermodynamic and kinetic conditions for inclusion removal.

[0023] S1. The number of eccentric auxiliary gas nozzles in the pretreatment and multi-parameter online detection deployment is 4-6. The nozzle axis forms an angle of 15-30° with the tangent direction of the inner wall of the riser. The auxiliary gas flow rate is 10-15% of the main booster gas flow rate. This structural parameter can form a stable and moderately strong swirling field in the riser, which not only ensures the mixing effect of molten steel, but also prevents molten steel from splashing and secondary oxidation due to excessive swirling intensity.

[0024] S1. The dynamic anti-nodulation composite coating in the pretreatment and multi-parameter online detection deployment consists of a MgO-Cr2O3-ZrO2 ternary matrix and an active functional layer doped with TiO2 and CeO2. During the rapid decarburization stage, the high temperature of the molten steel activates the high-temperature resistance and anti-oxidation function, and during the transition stage, the self-cleaning function is activated by injecting a small amount of air. The MgO-Cr2O3-ZrO2 ternary matrix has excellent high-temperature resistance and anti-corrosion properties. The doped TiO2 and CeO2 active components can be selectively activated under different conditions to achieve high-temperature resistance, anti-oxidation and self-cleaning functions, respectively, which extends the service life of the impregnated tube by 30%-40%.

[0025] S3. The mass ratio of the three batches of the gradient component composite refining agent in the precise pulse injection based on the real-time flow field is as follows: the first gradient is CaO-CaF2-Al2O3 pre-melted slag 7:2:1, the second gradient adds 5%-8% Ce and 2%-3% La, and the third gradient adds 3%-5% MgO and 1%-2% CaSi. The gradient component design can play a targeted role in the refining agent according to the type and size of inclusions at different stages, avoiding the single-function defect of single component refining agents and significantly improving the overall refining effect of the refining agent.

[0026] S3. Based on real-time flow field, the precise pulse injection of graded argon microbubbles is divided into two stages. The first stage, with a diameter of 50-100μm, is used to capture ultrafine inclusions <10μm, and the second stage, with a diameter of 100-200μm, is used to capture fine inclusions 10-20μm. The volume ratio of the two stages of microbubbles is 1:1. The graded particle size design can achieve precise capture of inclusions of different sizes, solving the industry problem of low capture efficiency of ultrafine inclusions by traditional single-size microbubbles, and greatly improving the removal rate of fine inclusions <20μm.

[0027] S3. The pulsed alternating injection sequence in the precise pulse injection based on real-time flow field is as follows: after injecting the refining agent for 5-10 seconds, there is an interval of 10-15 seconds, followed by the injection of microbubbles for 10-15 seconds. The total amount of refining agent injected is 1.5-2.5 kg / t steel, and the total amount of microbubbles injected is 0.3-0.5 Nm³ / t steel. This injection sequence enables the refining agent and microbubbles to form a continuous process of "adsorption-modification-capture-floatation" in the molten steel, avoiding mutual interference caused by the simultaneous injection of refining agent and microbubbles. The total injection amount is optimized, which can reduce the consumption of refining agent and production costs while ensuring the refining effect.

[0028] S1, the directional flow guidance structure in the pretreatment and multi-parameter online detection deployment consists of 4-6 arc-shaped guide plates. The guide plates form an angle of 30-45° with the bottom of the vacuum chamber, and the height is 1 / 8-1 / 6 of the height of the vacuum chamber. The radius of curvature is consistent with the bottom of the vacuum chamber. The structural parameters can perfectly match the direction of the molten steel circulation constructed by S2, forming an efficient directional floating channel for inclusions, which increases the floating speed of inclusions by more than 40%, and effectively eliminates the circulation dead zone at the bottom of the vacuum chamber.

[0029] S2. In the rapid decarburization stage of phased gradient vacuum-lifting gas synergistic control, when the initial oxygen content of the molten steel is <500ppm, oxygen is injected through the oxygen lance at the top of the vacuum chamber at a flow rate of 50-80Nm³ / h for 2-3 minutes. This can accurately replenish the oxygen potential required for the decarburization reaction, avoid the decrease in decarburization rate and incomplete decarburization caused by insufficient oxygen content, and ensure the treatment effect of the rapid decarburization stage.

[0030] S4. In the process of dynamic control of purity and tapping, the total oxygen content of the treated molten steel is ≤5ppm, the removal rate of ultrafine inclusions <10μm is ≥75%, the removal rate of fine inclusions <20μm is ≥90%, the spheroidization rate of inclusions is ≥95%, and the total recovery rate of rare earth elements is ≥75%. These indicators are far superior to the traditional RH refining process, which can meet the stringent requirements of high-end fields such as aerospace, wind power, and rail transportation for the purity of special steel, and significantly improve the fatigue life and impact resistance of special steel.

[0031] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An optimized process for high-purity special steel RH vacuum refining, characterized in that, include: S1. Preprocessing and multi-parameter online detection deployment: A laser-induced breakdown spectroscopy online component analyzer is installed at the top of the RH vacuum chamber. Temperature sensors and electromagnetic flowmeters are installed at the inlet and outlet of the impregnation tube. An online inclusion monitor is installed on the side wall of the vacuum chamber. The riser tube is set as a variable diameter structure with the lower diameter being 15%-20% larger than the upper diameter. Eccentric auxiliary gas nozzles are evenly arranged around the circumference of the inner wall of the riser tube. A dynamic anti-nodulation composite coating that can be activated online is applied to the inner wall of the impregnation tube. An arc-shaped directional flow guide structure matching the direction of molten steel circulation is installed at the bottom of the vacuum chamber. S2. Staged gradient vacuum-lift gas coordinated control: The RH treatment process is divided into three continuous stages: rapid decarburization, transition, and purity control. Based on the real-time collected data on the carbon content, oxygen content, and temperature of the molten steel, the vacuum level and gas flow rate are dynamically adjusted. In the rapid decarburization stage, the vacuum level is rapidly reduced and the eccentric auxiliary gas nozzle is opened to form an axial swirling flow field, while activating the high-temperature resistance and oxidation resistance of the coating. In the transition stage, the vacuum level is gradually increased and the gas flow rate is reduced to activate the self-cleaning function of the coating. In the purity control stage, a mild and stable molten steel circulation is maintained. S3. Precise pulse injection based on real-time flow field: By utilizing the uniform and stable molten steel flow field constructed in the S2 staged gradient vacuum-lifting gas coordinated control, combined with real-time collected flow velocity and flow rate data, two optimal injection points are dynamically determined in the lower part of the riser and the bottom circulation zone of the vacuum chamber. At the end of the transition stage, gradient component composite refining agent and graded particle size argon microbubbles are injected alternately in a pulsed manner through the two injection points. First, the first gradient pre-melted slag refining agent and the first-stage microbubbles are injected to adsorb large inclusions. Then, the second gradient refining agent containing rare earth elements and the second-stage microbubbles are injected to modify and capture fine inclusions. Finally, the third gradient refining agent containing MgO is injected to refine and spherize the inclusions. S4. Dynamic control of purity and steel tapping: During the purity control stage, the pulse injection parameters are adjusted based on the online monitoring data of inclusions, and a directional flow guide structure at the bottom of the vacuum chamber is used to construct a directional upward floating channel for inclusions until the purity of the molten steel meets the standard. After pure circulation treatment, the vacuum is broken and the steel is discharged.

2. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: In the S2 phase of the phased gradient vacuum-lift gas coordinated control, the vacuum level in the rapid decarburization stage is 67-133 Pa, and the lift gas flow rate is 120-150 Nm³ / h; the vacuum level in the transition stage is 200-300 Pa, and the lift gas flow rate is 80-100 Nm³ / h; and the vacuum level in the purity control stage is 400-500 Pa, and the lift gas flow rate is 50-70 Nm³ / h.

3. The optimized RH vacuum refining process for high-purity special steel according to claim 1, characterized in that: The number of eccentric auxiliary gas nozzles in the S1, pretreatment and multi-parameter online detection deployment is 4-6, the nozzle axis is at an angle of 15-30° with the tangent direction of the inner wall of the riser, and the auxiliary gas flow rate is 10-15% of the main booster gas flow rate.

4. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: The dynamic anti-nodulation composite coating described in S1, pretreatment and multi-parameter online detection deployment consists of a ternary matrix of MgO-Cr2O3-ZrO2 and an active functional layer doped with TiO2 and CeO2. During the rapid decarburization stage, the high temperature resistance and anti-oxidation function is activated by the high temperature of molten steel, and during the transition stage, the self-cleaning function is activated by the injection of a small amount of air.

5. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: The mass ratio of the three batches of the gradient component composite refining agent in S3, which is based on the precise pulse injection of the real-time flow field, is as follows: the first gradient is CaO-CaF2-Al2O3 pre-melted slag 7:2:1, the second gradient adds 5%-8%Ce and 2%-3%La, and the third gradient adds 3%-5%MgO and 1%-2%CaSi.

6. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: The graded argon microbubbles in S3, which are based on the real-time flow field for precise pulse injection, are divided into two stages. The first stage has a diameter of 50-100μm and is used to capture ultrafine inclusions of <10μm. The second stage has a diameter of 100-200μm and is used to capture fine inclusions of 10-20μm. The volume ratio of the two stages of microbubbles is 1:

1.

7. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: The pulsed alternating injection sequence in S3, based on real-time flow field precision pulse injection, is as follows: after injecting the refining agent for 5-10 seconds, there is an interval of 10-15 seconds, followed by the injection of microbubbles for 10-15 seconds. The total amount of refining agent injected is 1.5-2.5 kg / t steel, and the total amount of microbubbles injected is 0.3-0.5 Nm³ / t steel.

8. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: The directional flow guidance structure described in S1, preprocessing, and multi-parameter online detection deployment consists of 4-6 arc-shaped flow guide plates. The flow guide plates form an angle of 30-45° with the bottom of the vacuum chamber, and their height is 1 / 8-1 / 6 of the height of the vacuum chamber. The radius of curvature is consistent with the bottom of the vacuum chamber.

9. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: In the rapid decarburization stage of the phased gradient vacuum-lifting gas coordinated control in S2, when the initial oxygen content of the molten steel is <500ppm, oxygen is injected through the oxygen lance at the top of the vacuum chamber at a flow rate of 50-80Nm³ / h for 2-3 minutes.

10. The optimized process for high-purity special steel RH vacuum refining according to claim 1, characterized in that: In the S4 process, the purity dynamic control and steel tapping process, the total oxygen content of the treated molten steel is ≤5ppm, the removal rate of <10μm ultrafine inclusions is ≥75%, the removal rate of <20μm fine inclusions is ≥90%, the inclusion spheroidization rate is ≥95%, and the total recovery rate of rare earth elements is ≥75%.

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