Low-phosphorus steel converter whole-process automatic control smelting method

Abstract

The present application belongs to the technical field of steel smelting, and specifically discloses a low-phosphorus steel converter full-process automatic control smelting method, which lays a stable dephosphorization foundation by strict control of molten iron and slag-making materials into the furnace; a low-temperature, high-FeO and high-alkalinity slag environment is created by high gun position, low oxygen supply and weak bottom blowing in the early stage to quickly complete pre-dephosphorization; in the middle stage, homogenization of the slag and inhibition of phosphorus reversion are realized by medium gun position, strong bottom blowing and full-amount slag-making material addition; the TSC auxiliary gun detects the molten pool state in real time, the limestone addition amount is calculated through a dynamic thermodynamic model, and the process temperature and alkalinity are precisely fine-tuned; long-time carbon pulling and blowing is performed at the endpoint by using ultra-low gun position, high oxygen supply and strong bottom blowing, and nitrogen blowing and weak stirring are cooperated, deep dephosphorization is realized under the conditions of high final slag alkalinity and high endpoint oxygen, and finally the control requirements of no tapping and no sample equalization for direct tapping are met.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, specifically to a fully automated control method for low-phosphorus steel converter smelting. Background Technology

[0002] Phosphorus is a harmful element in steel, which can cause "cold brittleness" and reduce the low-temperature impact toughness of steel. Low-phosphorus steel, with an endpoint phosphorus mass fraction of ≤0.008% and a finished product phosphorus mass fraction of <0.012%, has become the basic raw material for core varieties such as high-end plates and special structural steel. Its stable, efficient and low-cost smelting technology is the key for steel companies to upgrade their product structure and enhance their core market competitiveness.

[0003] Currently, converter steelmaking is the mainstream process for the industrial production of low-phosphorus steel in my country, and the industry has successively developed a variety of technical routes suitable for low-phosphorus steel smelting. Among them, the dual-slag method achieves segmented dephosphorization by pouring out the high-phosphorus slag from the early stage, which can achieve a certain degree of deep dephosphorization effect; the high-pulling and supplementary blowing method adjusts the final composition and temperature by high-pulling carbon and supplementary blowing, which is a common method for low-phosphorus steel smelting in most converters in China; the auxiliary lance dynamic control technology realizes dynamic adjustment of smelting parameters through process temperature measurement and sampling, which has been widely used in large converters in China, and the supporting general-purpose automatic steelmaking model has also been widely used.

[0004] Existing low-phosphorus steel smelting technologies still suffer from multiple technical shortcomings and bottlenecks, failing to meet the demands of large-scale production. In the initial pre-dephosphorization stage, problems commonly arise such as insufficient ferrous oxide content in the slag, slow lime melting, and excessively rapid heating of the molten pool, disrupting the core conditions for low-temperature dephosphorization and resulting in severely inadequate pre-dephosphorization effects. In the final control stage, furnace tilting for temperature measurement and sampling, along with waiting for composition results, significantly prolongs the smelting cycle. Furthermore, supplementary blowing dephosphorization exacerbates furnace lining erosion and deteriorates steel properties, thus restricting the production efficiency and quality stability of low-phosphorus steel smelting. Summary of the Invention

[0005] The purpose of this invention is to provide a fully automated control method for the smelting of low-phosphorus steel in a converter, in order to solve the problem that the pre-dephosphorization process in the prior art is not effective enough, which prolongs the smelting cycle and leads to the deterioration of steel performance.

[0006] To achieve the above objectives, the basic solution provided by this invention is: a fully automated control smelting method for low-phosphorus steel in a converter, comprising low-phosphorus steel with a final [P] mass fraction ≤0.008% and a finished product [P] mass fraction <0.012%, and further including raw material pretreatment and furnace feed control, pre-dephosphorization blowing, slag-retaining phosphorus blowing, auxiliary lance detection and dynamic control, deep dephosphorization and automatic tapping, the specific contents of which are as follows: Raw material pretreatment and furnace charge control: control the temperature of molten iron entering the furnace to ≤1360℃, the mass fraction of [P] in molten iron to <0.120%, the mass fraction of [Si] to 0.30%-0.60%, and the slag-forming materials entering the furnace to include highly active lime, lightly calcined magnesite, limestone, and high FeO cold-solidified pellets; Pre-dephosphorization blowing: After starting the blowing process, the oxygen step is 0%-5%, using a high lance position and low oxygen supply intensity, while the bottom blowing argon flow rate is controlled at 200-220 m³ / h. 3 / h, when the oxygen step reaches 3%, add 85%-90% of the total lime, 75%-80% of the total light-burned magnesite, and 100% cold-fixing pellet coolant. Slag-retaining phosphorus blowing: In the oxygen step range of 5%-45%, blowing is carried out using a medium gun position and medium oxygen supply intensity, while simultaneously increasing the bottom blowing argon flow rate. In the oxygen step range of 40%-45%, the remaining lime and lightly calcined magnesite are added. Sub-lance detection and dynamic control: Within the oxygen step range of 45%-85%, low-lance position blowing is adopted to maintain a stable bottom-blown argon flow rate; at 85% oxygen step, the real-time carbon content, temperature, and phosphorus content of the molten pool are detected by the TSC sub-lance. Based on the target value, the amount of limestone to be added is calculated by a dynamic thermodynamic model. At 87% oxygen step, limestone is added as a cooling and basicity regulator, and the molten pool heating rate is controlled in a closed loop to be ≤10℃ / min until the oxygen step reaches 95%. Deep dephosphorization and automatic steel tapping: Oxygen step 95%-100%, using ultra-low lance position and high oxygen supply intensity for final carbon removal blowing, blowing time ≥120s, simultaneously increasing bottom blowing argon to high flow rate and strong stirring, controlling the final molten pool temperature ≤1610℃, carbon mass fraction ≤0.035%, and final slag basicity 3.9-4.3; after the blowing endpoint is reached, switch the top blowing medium to nitrogen for slag surface purging and weak stirring, and after purging, without tilting the furnace or unequal sample, directly execute automatic steel tapping.

[0007] The working principle of this invention is as follows: This method aims at deep dephosphorization of low-phosphorus steel and operates according to the fully automated control logic of pre-dephosphorization-slag-phosphorus retention-dynamic regulation-deep dephosphorization. First, a stable dephosphorization foundation is established through strict control of molten iron and slag-forming materials entering the furnace. In the early stage, a low-temperature, high-FeO, and high-basicity slag environment is created by using a high lance position, low oxygen supply, and weak bottom blowing to quickly complete pre-dephosphorization. In the middle stage, slag homogenization and phosphorus reversion are achieved by using a medium lance position, strong bottom blowing, and the addition of the full amount of slag-forming materials. The TSC auxiliary lance monitors the molten pool status in real time and calculates the amount of limestone added through a dynamic thermodynamic model to precisely fine-tune the process temperature and basicity. At the end, long-term carbon-pulling and blowing are carried out with ultra-low lance position, high oxygen supply, and strong bottom blowing, combined with nitrogen purging and weak stirring, to achieve deep dephosphorization under high final slag basicity and high final oxygen conditions, ultimately meeting the control requirements of direct tapping of steel without furnace tilting and unequal sample tapping.

[0008] The beneficial effects of this invention are as follows: This method significantly improves the dephosphorization efficiency, quality stability, and production efficiency of low-phosphorus steel smelting through standardized and automated collaborative control of the entire process. It can stably control the final phosphorus content below 0.008% and the finished phosphorus content within 0.012%, and greatly improve the dephosphorization rate of the TSC process and the final dephosphorization rate. The entire process adopts automatic model control, eliminating reliance on manual experience, resulting in strong operational consistency and small quality fluctuations. It eliminates the need for furnace tilting for temperature measurement and sampling and waiting for composition results, saving the blowing stage, effectively shortening the smelting cycle, reducing material consumption and furnace lining erosion, and improving converter operation rate and intelligent production level.

[0009] Option 2, which is the preferred option of the basic option, involves the following raw material pretreatment and furnace feed control: effective calcium oxide content of lime ≥90%, CO2 content of limestone ≥42%, MgO content of light-burned magnesite ≥30%, and FeO content of cold-set pellets ≥28%. The total amount of lime added is calculated thermodynamically based on the target basicity of the final slag of 4.0±0.2. The total amount of light-burned magnesite added is calculated based on the MgO mass fraction of the final slag of 9%±1%. The total amount of cold-set pellets added is 1.5%-3.0% of the amount of molten iron charged.

[0010] Option 3, the preferred option of the basic scheme, involves a high lance position of 2300mm-2500mm and an oxygen supply intensity of 3.0-3.1m during pre-dephosphorization blowing. 3 / (t·min), the slag FeO content is fed back in real time by the flame spectrum detection at the furnace mouth, and the gun position and oxygen supply intensity are adjusted in a closed loop to maintain the slag FeO mass fraction of 18%-25% and the molten pool heating rate ≤15℃ / min.

[0011] Option 4, the preferred option of the basic scheme, involves a central lance position of 1500mm-1700mm and an oxygen supply intensity of 3.3-3.4m during slag-retaining phosphorus blowing. 3 / (t·min), bottom-blown argon flow rate is 320-340m³ 3 / h, the slag formation status is detected and fed back in real time by sonar in the molten pool, and the lance position is adjusted in a closed loop to maintain the slag basicity of 3.0-3.5 and the MgO mass fraction of 8%-10%.

[0012] Option 5, the preferred option of the basic option, involves secondary gun detection and dynamic control with a low gun position of 1200mm-1400mm and an oxygen supply intensity of 3.1-3.2m. 3 The amount of limestone added, per t / min, is calculated using the following formula: Limestone addition amount = (TSC measured temperature - target process temperature) × molten pool heat capacity / limestone cooling effect value; The target process temperature is 1520℃~1540℃, the limestone cooling effect is 0.72-0.75kWh / kg, and when the measured [P] mass fraction of TSC is >0.030%, an additional 150kg-300kg of limestone is added.

[0013] Option 6, the preferred option of the basic scheme, involves deep dephosphorization and automatic steel tapping, with an ultra-low lance position of 900mm-1100mm and an oxygen supply intensity of 3.4-3.5m. 3 / (t·min), bottom-blown argon flow rate is 360-380m 3 / h; endpoint control: carbon-oxygen product ≤ 0.0024%, slag FeO mass fraction ≥ 28%; nitrogen purging gas supply intensity: 4.5-5.0m 3 / (t·min), gun position distance from liquid surface 3800mm-4200mm, purging time 10s-18s.

[0014] Option 7, an optimal choice from Option 6, involves bottom blowing with a pulsed, high-stirring mode during the final carbon extraction process. Each cycle lasts 30 seconds, with the flow rate maintained at 360-380 m³ / h for the first 20 seconds. 3 / h, then drops to 240-260m in the last 10 seconds. 3 / h; During the automatic tapping process, when 1 / 3 of the steel is tapped, ladle refining slag with an alkalinity ≥5.0 is added at 2.5-3.0 kg / t to control the increase in phosphorus return during tapping to ≤0.003%.

[0015] Option 8 is the preferred option of Option 3. The closed-loop adjustment logic for FeO in the pre-dephosphorization slag is as follows: the total amount of lime added is calculated thermodynamically based on the target basicity of the final slag of 4.0±0.2; the total amount of light-burned magnesite added is calculated based on the MgO mass fraction of the final slag of 9%±1%; and the total amount of cold-solidified pellets added is 1.5%-3.0% of the amount of molten iron charged.

[0016] Option 9, an optimal choice of Option 4, uses the following closed-loop adjustment logic for slag formation: if the sonar detection value exceeds a set threshold, it indicates slag drying; in this case, the lance position is raised by 100mm-150mm, and the oxygen supply intensity is reduced by 0.1-0.15m. 3 / (t·min); If the sonar detection value is lower than the set threshold, it is determined that the slag is excessively foamed, and the gun position is lowered by 100-150mm and the oxygen supply intensity is increased by 0.1-0.15m. 3 / (t·min). Attached Figure Description

[0017] Figure 1 This is a flowchart of a fully automated control smelting method for low-phosphorus steel in a converter according to the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below through specific embodiments: Example like Figure 1 The present invention discloses a fully automated control method for the smelting of low-phosphorus steel in a converter, comprising methods for producing low-phosphorus steel with a final [P] mass fraction ≤0.008% and a finished product [P] mass fraction <0.012%, and further including raw material pretreatment and furnace feed control, pre-dephosphorization blowing, slag-forming and phosphorus-preserving blowing, auxiliary lance detection and dynamic control, deep dephosphorization and automatic tapping, as detailed below: Raw material pretreatment and furnace charge control: The temperature of the molten iron charged into the furnace is controlled to be ≤1360℃, the mass fraction of [P] in the molten iron is <0.120%, and the mass fraction of [Si] is 0.30%-0.60%. The slag-forming materials charged into the furnace include highly active lime, light-burned magnesite, limestone, and high-FeO cold-fixed pellets. The effective calcium oxide content of the lime is ≥90%, the CO2 content of the limestone is ≥42%, the MgO content of the light-burned magnesite is ≥30%, and the FeO content of the cold-fixed pellets is ≥28%. The total amount of lime added is calculated thermodynamically based on the target basicity of the final slag of 4.0±0.2. The total amount of light-burned magnesite added is calculated based on the MgO mass fraction of the final slag of 9%±1%. The total amount of cold-fixed pellets added is 1.5%-3.0% of the molten iron charge. Pre-dephosphorization blowing: After the initial blowing, the oxygen step is 0%-5%, using a high lance position of 2300mm-2500mm and a depth of 3.0-3.1m. 3 / (t·min) Low oxygen supply intensity blowing, while bottom blowing argon flow rate is controlled at 200-220m³ / t. 3 When the oxygen content reaches 3%, add 85%-90% of the total lime content, 75%-80% of the total light-burned magnesite content, and 100% cold-solidified pellet coolant. Real-time feedback on slag FeO content is obtained through furnace mouth flame spectroscopy. The lance position and oxygen supply intensity are adjusted in a closed loop to maintain a slag FeO mass fraction of 18%-25% and a molten pool heating rate ≤15℃ / min. The closed-loop adjustment logic for slag FeO in the pre-dephosphorization stage is as follows: the total lime content is calculated thermodynamically based on the final slag target basicity of 4.0±0.2; the total light-burned magnesite content is calculated based on a final slag MgO mass fraction of 9%±1%; and the total cold-solidified pellet addition is 1.5%-3.0% of the molten iron charge. Slag-retaining phosphorus blowing: Within the oxygen step range of 5%-45%, use a 1500mm-1700mm lance position and a depth of 3.3-3.4m. 3 The oxygen supply intensity is increased at / (t·min) for refining, and the bottom blowing argon flow rate is simultaneously increased to 320-340m³. 3At a rate of 40%-45% oxygen content, the remaining lime and lightly calcined magnesite are added. The slag formation status is monitored in real-time using sonar in the molten pool. The lance position is adjusted in a closed-loop manner to maintain a slag basicity of 3.0-3.5 and an MgO mass fraction of 8%-10%. The closed-loop adjustment logic for the slag formation status is as follows: if the sonar detection value exceeds a set threshold, it is considered slag drying, and the lance position is raised by 100mm-150mm, while the oxygen supply intensity is reduced by 0.1-0.15m. 3 / (t·min); If the sonar detection value is lower than the set threshold, it is determined that the slag is excessively foamed, and the gun position is lowered by 100-150mm and the oxygen supply intensity is increased by 0.1-0.15m. 3 / (t·min); Sub-lance testing and dynamic control: Within the oxygen step range of 45%-85%, use a low-position blowing lance (1200mm-1400mm) to maintain a stable bottom-blown argon flow rate of 3.1-3.2m³. 3 / (t·min), when the oxygen step reaches 85%, the real-time carbon content, temperature, and phosphorus content of the molten pool are detected by the TSC sub-lance. Based on the endpoint target value, the amount of limestone added is calculated using a dynamic thermodynamic model. Limestone is added at 87% of the oxygen step as a cooling and alkalinity regulator. The closed-loop control of the molten pool heating rate is ≤10℃ / min until the oxygen step reaches 95%. The amount of limestone added is calculated according to the following formula: Limestone addition amount = (TSC measured temperature - target process temperature) × molten pool heat capacity / limestone cooling effect value The target process temperature is 1520℃~1540℃, the limestone cooling effect is 0.72-0.75kWh / kg, and when the measured [P] mass fraction of TSC is >0.030%, an additional 150kg-300kg of limestone is added. Deep dephosphorization and automated steel tapping: oxygen step 95%-100%, using an ultra-low lance position of 900mm-1100mm and a depth of 3.4-3.5m. 3 At the final stage of carbon extraction, high oxygen supply intensity is applied for carbon blowing, with a blowing time ≥120s, and the bottom blowing argon gas is simultaneously increased to 360-380m. 3 With vigorous stirring, control the final molten pool temperature to ≤1610℃, carbon mass fraction to ≤0.035%, and final slag basicity to 3.9-4.3; after reaching the blowing endpoint, switch the top blowing medium to nitrogen for slag surface purging and weak stirring. After purging, automatically tap the steel without tilting the furnace or unequalizing the sample; control the carbon-oxygen product to ≤0.0024% and the slag FeO mass fraction to ≥28%; the nitrogen purging gas supply intensity is 4.5-5.0 m³ / h. 3 / (t·min), gun position distance from liquid surface 3800mm-4200mm, purging time 10s-18s, during the final carbon pulling and blowing, bottom blowing adopts pulse strong stirring mode, with each cycle being 30s, of which the flow rate is maintained at 360-380m³ / min for the first 20s. 3 / h, then drops to 240-260m in the last 10 seconds. 3 / h; During the automatic tapping process, when 1 / 3 of the steel is tapped, ladle refining slag with an alkalinity ≥5.0 is added at 2.5-3.0 kg / t to control the increase in phosphorus return during tapping to ≤0.003%.

[0019] The implementation method of this embodiment is as follows: A 120t top-and-bottom blown converter was used. Argon was used as the bottom blowing medium throughout the smelting process, with nitrogen used only during the slag splashing and furnace protection stage. The target steel grade to be smelted was low-phosphorus structural steel with a final [P] mass fraction ≤0.008% and a finished product [P] mass fraction <0.012%. The total charge for this smelting was precisely controlled at 120.0t, including 106.2t of molten iron and 13.8t of scrap steel. The scrap steel used was a mixture of 8.5t of heavy scrap steel and 5.3t of high-quality briquetted scrap steel, without the addition of pig iron blocks. The measured temperature of the molten iron entering the furnace after being transferred through a torpedo ladle was 1348℃. The measured values ​​of the molten iron composition spectrum were w[C]=4.32%, w[Si]=0.42%, w[Mn]=0.28%, w[P]=0.108%, and w[S]=0.012%, which fully met the furnace charge control requirements.

[0020] Before smelting, the slag-forming materials are accurately weighed and prepared. The specific indicators and quantities of the slag-forming materials are as follows: 4380 kg of high-activity lime with an effective calcium oxide content of 92.3%, 1080 kg of light-burned magnesite with an MgO content of 32.7%, 2120 kg of cold-solidified pellets with a TFe content of 58.2% and an FeO content of 30.5%, and limestone with a CO2 content of 43.6% and an effective calcium oxide content of 52.1% is reserved as a process cooling and basicity regulator. The total amount of lime added is determined by thermodynamic calculation based on the target basicity of 4.0 for the final slag. The total amount of light-burned magnesite added is determined by calculation based on the MgO mass fraction of 9% for the final slag. The total amount of cold-solidified pellets added is determined by 2.0% of the amount of molten iron charged.

[0021] During smelting, after the converter is rocked to zero and equipment and safety checks are completed before blowing begins, the oxygen supply system is started and blowing officially begins. After blowing begins, the oxygen level is maintained between 0% and 5%, the initial position of the oxygen lance is precisely controlled at 2400mm, and the oxygen supply flow rate is stabilized at 26500Nm³. 3 / h, corresponding to an oxygen supply intensity of 3.05m 3 / (t·min), while the bottom-blown argon flow rate is constantly controlled at 210m³. 3 / h; During the initial blowing process, the furnace mouth flame spectrum data is collected in real time by the furnace mouth flame spectrum detection system. The slag FeO content is calculated online, and the lance position and oxygen supply intensity are adjusted in a closed loop. After 30 seconds of initial blowing, the system detects that the slag FeO mass fraction is 17.2%, which is lower than the control limit of 18%. The oxygen lance position is immediately raised by 80mm to 2480mm, and the oxygen supply flow rate is reduced to 26000Nm. 3At 50 seconds after the start of blowing, the system detected that the FeO mass fraction in the slag had rebounded to 20.6%, returning to the control range and maintaining stable operation with the adjusted parameters. When the oxygen step reached 3%, corresponding to 43 seconds of blowing, the first batch of slag was added smoothly in two batches through the high-level silo. The first batch consisted of 3850 kg of lime and 840 kg of lightly calcined magnesite. After a 12-second interval, all 2120 kg of cold-solidified pellets were added. No splashing occurred in the furnace throughout the process. During this stage, the heating rate of the molten pool was controlled at 12.5℃ / min. When the oxygen step reached 5%, corresponding to 72 seconds of blowing, the real-time temperature of the molten pool was 1378℃. The process model calculated that the phosphorus mass fraction in the molten pool had decreased to 0.024%, completing the initial pre-dephosphorization.

[0022] The oxygen supply level was adjusted to between 5% and 45%, the oxygen lance position was precisely lowered to 1600mm, and the oxygen flow rate was adjusted to 29000Nm. 3 / h, corresponding to an oxygen supply intensity of 3.35m 3 / (t·min), simultaneously increase the bottom-blown argon flow rate to 330m 3 / h; In this stage, the sonar signal inside the furnace is collected in real time by the molten pool sonar detection system to provide feedback on the slag formation status and adjust the lance position and oxygen supply intensity in a closed loop. 200s after blowing begins, the system detects that the sonar value exceeds the set threshold, which is determined to be slag drying. The oxygen lance position is immediately raised by 120mm to 1720mm, and the oxygen supply flow rate is reduced to 28000Nm³. 3 / h, after 230 seconds of blowing, the system detected that the sonar value had returned to the normal range, so the oxygen lance position was lowered to 1600mm, and the oxygen supply flow rate was restored to 29000Nm. 3 The process maintained a stable slag basicity of 3.2 and a stable MgO mass fraction of 9.1% throughout the entire process, effectively suppressing phosphorus reversion in the molten pool. When the oxygen step reached 42%, corresponding to 605 seconds of blowing, two batches of slag material were added at once through the high-level silo, namely the remaining 530 kg of lime and 240 kg of lightly calcined magnesite, completing the feeding of all slag-forming materials into the furnace. When the oxygen step reached 45%, corresponding to 648 seconds of blowing, the slag was completely smelted. The process model calculated that the carbon mass fraction in the molten pool was 1.18%, the molten pool temperature was 1476℃, and the phosphorus mass fraction in the molten pool was 0.021%, with no phosphorus reversion occurring.

[0023] The oxygen supply level was adjusted to between 45% and 85%, the oxygen lance position was precisely lowered to 1300mm, and the oxygen flow rate was adjusted to 27300Nm. 3 / h, corresponding to an oxygen supply intensity of 3.15m 3 / (t·min), maintain bottom-blown argon flow rate at 330m³ / (t·min), 3The temperature of the molten pool was kept stable at a constant h, and the blowing process was carried out smoothly to control the uniform temperature rise of the molten pool. When the oxygen step reached 85%, blowing was started for 1224 seconds. The TSC auxiliary lance was automatically lowered and inserted into the molten pool to complete the test. The measured data of the molten pool were obtained as follows: [C] mass fraction 0.41%, temperature 1548℃, and [P] mass fraction 0.031%. The test data were input into the dynamic thermodynamic model, with 1530℃ as the target process temperature. Combined with the molten pool heat capacity of 1.21kWh / (t·℃) and the limestone cooling effect of 0.73kWh / kg, the basic amount of limestone added was calculated to be 3578kg. At the same time, due to the measured phosphorus in the molten pool... If the mass fraction is higher than 0.030%, an additional 200 kg of limestone is added, and the total amount of limestone added is finally determined to be 3778 kg. The actual amount of material weighed and prepared on site is 3780 kg. When the oxygen step reaches 87%, blowing is started for 1253 seconds. The oxygen lance position is slightly adjusted to 1350 mm, and all 3780 kg of limestone is added at once through the high-level silo. After the addition is completed, the closed-loop control of the molten pool heating rate is 8.2℃ / min, and the blowing is stable until the oxygen step reaches 95%. At this time, the process model calculates the molten pool temperature to be 1598℃, the carbon mass fraction to be 0.078%, and the phosphorus mass fraction to be 0.011%.

[0024] The oxygen supply level reached 95% to 100%, the oxygen lance position was precisely lowered to 1000mm, and the oxygen flow rate was increased to 29900Nm. 3 / h, corresponding to an oxygen supply intensity of 3.45m 3 / (t·min), start the final carbon extraction blowing process, the total duration of carbon extraction blowing is 142s, which meets the control requirement of ≥120s. Simultaneously, switch the bottom blowing argon gas to pulsed strong stirring mode, with a cycle of 30s. In each cycle, maintain 370m for the first 20s. 3 The high flow rate of / h decreased to 250m in the following 10 seconds. 3 A low flow rate of [flow rate] / h was used to enhance mass transfer at the steel-slag interface to achieve deep dephosphorization. During this stage, the final molten pool parameters were strictly controlled. Oxygen supply was stopped when the oxygen step reached 100%. At the time of oxygen shutdown, the dynamic model, combined with TSC measured data, accurately calculated the molten pool state as follows: temperature 1603℃, carbon mass fraction 0.031%, carbon-oxygen product 0.0023%, final slag basicity 4.08, final slag FeO mass fraction 29.7%, and final phosphorus mass fraction 0.0058%, fully meeting the target control requirements. Immediately after oxygen shutdown, the top-blowing medium was switched to nitrogen, with the nitrogen supply flow rate controlled at 41800 Nm³. 3 / h, corresponding to a gas supply intensity of 4.8m 3 / (t·min), lower the oxygen lance to a position 4000mm above the molten pool surface, and purge and gently stir the slag surface. The purging time is precisely controlled to be 15s, and the bottom-blown argon gas is maintained at 370m during the purging process. 3The high flow rate of [flow rate] / h completes the final dephosphorization and slag treatment before tapping. After purging, the automatic tapping program is started directly by shaking the furnace without tilting or unequal sampling. The total tapping time is 3 minutes and 42 seconds, with a finished steel output of 118.6t and a steel recovery rate of 98.8%. During tapping, when the tapping volume reaches 1 / 3 of the total output, 300kg of ladle refining slag with a basicity of 5.2 is added to the ladle at a rate of 2.53kg / t. Throughout the process, the bottom blowing argon gas in the ladle is maintained at 50L / min with weak stirring to effectively suppress tapping. Phosphorus recovery during the process; after tapping, spectral analysis of samples taken from the ladle showed that the actual composition of the finished molten steel was w[C]=0.029%, w[Si]=0.22%, w[Mn]=0.45%, w[P]=0.0076%, and w[S]=0.008%. The mass fraction of [P] in the finished product was far below the control limit of 0.012%, and the phosphorus recovery increment during tapping was 0.0018%, which meets the control requirement of ≤0.003%. The entire process of low-phosphorus steel smelting in this heat was completed with automatic control, and all indicators met the standards.

[0025] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A fully automated control method for low-phosphorus steel converter smelting, characterized in that, This includes low-phosphorus steel used for smelting endpoints with a [P] mass fraction ≤0.008% and finished product [P] mass fraction <0.012%, as well as raw material pretreatment and furnace feed control, pre-dephosphorization blowing, slag-based phosphorus-preserving blowing, auxiliary lance detection and dynamic control, deep dephosphorization and automatic tapping. Specific details are as follows: Raw material pretreatment and furnace charge control: control the temperature of molten iron entering the furnace to ≤1360℃, the mass fraction of [P] in molten iron to <0.120%, the mass fraction of [Si] to 0.30%-0.60%, and the slag-forming materials entering the furnace to include highly active lime, lightly calcined magnesite, limestone, and high FeO cold-solidified pellets; Pre-dephosphorization blowing: After starting the blowing process, the oxygen step is 0%-5%, using a high lance position and low oxygen supply intensity, while the bottom blowing argon flow rate is controlled at 200-220 m³ / h. 3 / h, when the oxygen step reaches 3%, add 85%-90% of the total lime, 75%-80% of the total light-burned magnesite, and 100% cold-fixing pellet coolant. Slag-retaining phosphorus blowing: In the oxygen step range of 5%-45%, blowing is carried out using a medium gun position and medium oxygen supply intensity, while simultaneously increasing the bottom blowing argon flow rate. In the oxygen step range of 40%-45%, the remaining lime and lightly calcined magnesite are added. Sub-gun detection and dynamic control: Within the oxygen step range of 45%-85%, low-position blowing is adopted to maintain a stable bottom-blown argon flow rate; When the oxygen step reaches 85%, the real-time carbon content, temperature, and phosphorus content of the molten pool are detected by the TSC sub-lance. Based on the target value, the amount of limestone to be added is calculated using a dynamic thermodynamic model. When the oxygen step reaches 87%, limestone is added as a cooling and alkalinity regulator. The closed-loop control of the molten pool heating rate is ≤10℃ / min until the oxygen step reaches 95%. Deep dephosphorization and automatic steel tapping: Oxygen step 95%-100%, using ultra-low lance position and high oxygen supply intensity for final carbon removal blowing, blowing time ≥120s, simultaneously increasing bottom blowing argon to high flow rate and strong stirring, controlling the final molten pool temperature ≤1610℃, carbon mass fraction ≤0.035%, and final slag basicity 3.9-4.3; after the blowing endpoint is reached, switch the top blowing medium to nitrogen for slag surface purging and weak stirring, and after purging, without tilting the furnace or unequal sample, directly execute automatic steel tapping.

2. The fully automated control smelting method for low-phosphorus steel in a converter according to claim 1, characterized in that, In the raw material pretreatment and furnace charge control, the effective calcium oxide content of lime is ≥90%, the CO2 content of limestone is ≥42%, the MgO content of light-burned magnesite is ≥30%, and the FeO content of cold-set pellets is ≥28%. The total amount of lime added is calculated thermodynamically based on the target basicity of the final slag of 4.0±0.

2. The total amount of light-burned magnesite added is calculated based on the MgO mass fraction of the final slag of 9%±1%. The total amount of cold-set pellets added is 1.5%-3.0% of the amount of molten iron charged.

3. The fully automated control smelting method for low-phosphorus steel converters according to claim 1, characterized in that, During pre-dephosphorization blowing, the high lance position is 2300mm-2500mm, and the oxygen supply intensity is 3.0-3.1m. 3 / (t·min), the slag FeO content is fed back in real time by the flame spectrum detection at the furnace mouth, and the gun position and oxygen supply intensity are adjusted in a closed loop to maintain the slag FeO mass fraction of 18%-25% and the molten pool heating rate ≤15℃ / min.

4. The fully automated control smelting method for low-phosphorus steel in a converter according to claim 1, characterized in that, In the slag-retaining phosphorus blowing process, the intermediate lance position is 1500mm-1700mm, and the oxygen supply intensity is 3.3-3.4m. 3 / (t·min), bottom-blown argon flow rate is 320-340m³ 3 / h, the slag formation status is detected and fed back in real time by sonar in the molten pool, and the lance position is adjusted in a closed loop to maintain the slag basicity of 3.0-3.5 and the MgO mass fraction of 8%-10%.

5. The fully automated control smelting method for low-phosphorus steel in a converter according to claim 1, characterized in that, During secondary gun testing and dynamic control, the low gun position is 1200mm-1400mm, and the oxygen supply intensity is 3.1-3.2m. 3 The amount of limestone added, per t / min, is calculated using the following formula: Limestone addition amount = (TSC measured temperature - target process temperature) × molten pool heat capacity / limestone cooling effect value; The target process temperature is 1520℃~1540℃, the limestone cooling effect is 0.72-0.75kWh / kg, and when the measured [P] mass fraction of TSC is >0.030%, an additional 150kg-300kg of limestone is added.

6. The fully automated control smelting method for low-phosphorus steel in a converter according to claim 1, characterized in that, In deep dephosphorization and automatic steel tapping, the ultra-low lance position is 900mm-1100mm, and the oxygen supply intensity is 3.4-3.5m. 3 / (t·min), bottom-blown argon flow rate is 360-380m 3 / h; endpoint control: carbon-oxygen product ≤ 0.0024%, slag FeO mass fraction ≥ 28%; nitrogen purging gas supply intensity: 4.5-5.0m 3 / (t·min), gun position distance from liquid surface 3800mm-4200mm, purging time 10s-18s.

7. The fully automated control smelting method for low-phosphorus steel in a converter according to claim 6, characterized in that, During the final carbon blowing process, bottom blowing employs a pulsed, high-stirring mode, with each cycle lasting 30 seconds. The flow rate is maintained at 360-380 m³ / s for the first 20 seconds. 3 / h, then drops to 240-260m in the last 10 seconds. 3 / h; During the automatic tapping process, when 1 / 3 of the steel is tapped, ladle refining slag with an alkalinity ≥5.0 is added at 2.5-3.0 kg / t to control the increase in phosphorus return during tapping to ≤0.003%.

8. The fully automated control smelting method for low-phosphorus steel in a converter according to claim 3, characterized in that, The logic for completing the closed-loop adjustment of FeO in the pre-dephosphorization slag is as follows: the total amount of lime added is calculated thermodynamically based on the target basicity of the final slag of 4.0±0.2; the total amount of light-burned magnesite added is calculated based on the MgO mass fraction of the final slag of 9%±1%; and the total amount of cold-solidified pellets added is 1.5%-3.0% of the amount of molten iron charged.

9. The fully automated control smelting method for low-phosphorus steel in a converter according to claim 4, characterized in that, The closed-loop adjustment logic for slag formation is as follows: if the sonar detection value exceeds a set threshold, it is determined that the slag is drying out, the lance position is raised by 100mm-150mm, and the oxygen supply intensity is reduced by 0.1-0.15m. 3 / (t·min); If the sonar detection value is lower than the set threshold, it is determined that the slag is excessively foamed, and the gun position is lowered by 100-150mm and the oxygen supply intensity is increased by 0.1-0.15m. 3 / (t·min).

Images