A control method for improving the castability of a beam blank silicon killed steel

Abstract

The application provides a control method for improving the castability of a beam blank silicon killed steel, and the application establishes an intelligent argon blowing model at the end of a converter, combines dynamic deoxidation alloying, and matches top lime and fluorite to quickly form top slag with a certain basicity. The intelligent argon blowing system is used at the refining inlet to quickly form slag, the LIBS steel slag online detection system is used to quickly analyze the slag composition, a slag control model is established, and guidance is provided for the next step of slag adjustment. The calcium treatment in refining adopts hierarchical control, different package conditions and process control conditions are treated in stages, the recommended feeding amount of nano high-calcium wire is obtained through total oxygen calculation, a new type of seamless nano high-calcium wire is used to ensure the calcium yield, and after calcium treatment, the intelligent argon blowing system is switched to soft blowing mode to ensure the sufficient floating of inclusions. Different water inlets and slide block combinations are matched according to different billet types during continuous casting to ensure the stability of the casting process.

Description

Technical Field

[0001] This invention belongs to the field of converter steelmaking technology, and particularly relates to a method for controlling the pourability of molten silicon killed steel in shaped billets. Background Technology

[0002] Due to the complexity of the cross-section of shaped billets and the use of thin-web plate technology, continuous casting machines for special-shaped billets face significant challenges in stopper rod flow control, necessitating the use of sizing nozzles. However, the small diameter of these nozzles and the need for protective casting make them prone to nozzle clogging. Therefore, the castability of silicon-killed steel in shaped billets has consistently been a major obstacle to stable production. Numerous factors contribute to poor castability, and traditional control methods are often limited to specific stages and rely on the experience of on-site workers. This inevitably leads to inaccurate furnace condition assessments and unstable control levels, resulting in poor castability. To completely resolve the issue of castability in silicon-killed steel for special-shaped billets, a systematic, end-to-end control method is needed to replace conventional processes. This involves establishing various intelligent control models by integrating intelligent equipment at each stage, improving the stability and accuracy of the control process, preventing misjudgments or unstable control levels, stabilizing process control, improving the castability of silicon-killed steel in special-shaped billets, and saving production costs. Summary of the Invention

[0003] The purpose of this invention is to provide a control method for improving the castability of silicon-killed steel in shaped billets. The control method in this invention involves full-process control, designing various control models, and establishing a dynamic control system. This significantly improves the cleanliness of the silicon-killed steel in shaped billets, reduces nozzle clogging caused by poor steel cleanliness, greatly enhances the castability of the steel, and reduces material and energy consumption and labor intensity through precise control of each stage. It also stabilizes the casting speed and output of the continuous casting machine, playing a positive role in cost reduction, efficiency improvement, and production stability throughout the entire process.

[0004] This invention provides a method for controlling the castability of molten silicon killed steel in irregularly shaped billets, comprising the following steps:

[0005] A) After the smelting and blowing process is completed, a converter slag washing control model is established. Based on the carbon content and carbon removal at the end point, the type and amount of deoxidizer and slag washing materials are selected. The bottom blowing intensity is automatically adjusted by using the converter intelligent bottom blowing argon system in conjunction with the feeding sequence.

[0006] The converter slag washing control model is as follows, based on the amount of feed per furnace:

[0007] If the final carbon content is <0.04%, add 355-365 kg of silicon-calcium-barium, 60-65 kg of carbon powder, and 780-820 kg of top lime.

[0008] The final carbon content is ≥0.04% and <0.06%. Add 335-345 kg of silicon-calcium-barium, 45-50 kg of carbon powder, and 680-720 kg of top lime.

[0009] The final carbon content is ≥0.06% and <0.08%. Add 295-305 kg of silicon-calcium-barium, 30-35 kg of carbon powder, and 580-720 kg of top lime.

[0010] The final carbon content is ≥0.08% and <0.10%. Add 275-285 kg of silicon-calcium-barium, 15-20 kg of carbon powder, and 480-520 kg of top lime.

[0011] The final carbon content is ≥0.10%. Add 245-255 kg of silicon, calcium and barium, 0 kg of carbon powder, and 430-470 kg of top lime.

[0012] The bottom blowing intensity is set according to the following 6 control stages based on the actual steel tapping time:

[0013] 1) At the beginning of the tapping stage, the gas supply flow rate is 45-55 L / min and the gas supply time is 55-65 s;

[0014] 2) During the deoxidizer and alloy addition stage, the gas supply flow rate is 190-310 L / min and the gas supply time is 35-45 s;

[0015] 3) During the slagging agent addition stage, the gas supply flow rate is 140-210 L / min, and the gas supply time is 35-45 s;

[0016] 4) During the stage of impurity floating, the gas supply flow rate is 90-110 L / min and the gas supply time is 45-55 s;

[0017] 5) During the slag-blocking stage, the gas supply flow rate is 45-55 L / min, and the gas supply time is 45-55 s;

[0018] 6) During the post-blowing stage, the gas supply flow rate is 45-55 L / min, and the gas supply time is 55-65 s;

[0019] B) Rapid slag formation: After tapping, the molten steel enters the LF refining process. The argon blowing system uses the side-blowing mode. After stirring for 2 minutes, the argon blowing system enters the normal mode and is powered on to promote slag formation, thus completing the initial slag formation.

[0020] In the side-blowing mode, the argon flow rate is 400-500 L / min and the argon pressure is 1.0-1.8 MPa;

[0021] In the conventional mode, the argon flow rate is 100–200 L / min and the argon pressure is 0.4–0.6 MPa.

[0022] C) Slag adjustment: Use the LIBS steel slag online detection system to take slag samples for online detection. After the steel slag composition is detected, establish a slag control model. Based on the steel slag composition and slag material, the amount of deoxidizer added, calculate the final composition of the steel grade, and accurately predict and control the slag composition.

[0023] D) Calcium treatment and soft blowing: After refining, establish a dynamic control model for calcium treatment, calculate the required calcium wire feed amount based on the total aluminum, sulfur, total oxygen and residual calcium content in the molten steel, and use seamless nano high-calcium wire for calcium treatment. After the wire feeding is completed, switch the argon blowing system to soft blowing mode.

[0024] In the soft blowing mode, the argon flow rate is 50-100 L / min and the argon pressure is 0.2-0.3 MPa;

[0025] E) After smelting is completed, the combination of the top nozzle and slide block is designed according to the production section, and casting is carried out.

[0026] When the cross-section is BB1, the slider is 17.5mm and 18mm, the inlet is 23mm, and the pulling speed is controlled between 0.9 and 1.0m / min;

[0027] When the cross-section is BB2, the slider is 17mm and 17.5mm, the inlet is 21mm, and the pulling speed is controlled between 0.95 and 1.05m / min;

[0028] When the cross-section is BB3, the slider is 18mm and 18.5mm, the inlet is 23mm, and the pulling speed is controlled between 0.9 and 1.0m / min.

[0029] Preferably, the converter slag washing control model is as follows:

[0030] If the final carbon content is <0.04%, add 360 kg of silicon-calcium-barium, 63-64 kg of carbon powder, and 800 kg of top lime.

[0031] The final carbon content is ≥0.04% and <0.06%. Add 340 kg of silicon-calcium-barium, 48-50 kg of carbon powder, and 600 kg of top lime.

[0032] The final carbon content is ≥0.06% and <0.08%. Add 300kg of silicon, calcium and barium, 32-33kg of carbon powder, and 600kg of top lime.

[0033] The final carbon content is ≥0.08% and <0.10%. Add 280kg of silicon-calcium-barium, 16-18kg of carbon powder, and 500kg of top lime.

[0034] The final carbon content is ≥0.10%. Add 250 kg of silicon, calcium, and barium, 0 kg of carbon powder, and 450 kg of top lime.

[0035] Preferably, when the blowing process is completed but the temperature or composition does not meet the requirements, intermittent blowing is performed, with each intermittent blowing lasting 100m. 3 Add 30 kg of silicon, calcium, and barium.

[0036] Preferably, the argon bottom blowing flow rate is controlled according to the alloy content of the steel. Steel alloy content <1.2t is low alloy, steel alloy content ≥1.2t and <2.0t is medium alloy, and steel alloy content ≥2.0t is high alloy.

[0037] 1) At the beginning of the tapping stage, the gas supply flow rate is 45-55 L / min and the gas supply time is 55-65 s;

[0038] 2) During the deoxidizer and alloy addition stage, the gas supply flow rate for low alloys is 200L / min, the gas supply flow rate for medium alloys is 250L / min, and the gas supply flow rate for high alloys is 300L / min, with a gas supply time of 35-45s.

[0039] 3) During the slag-forming agent addition stage, the gas supply flow rate for low alloys is 150 L / min, the gas supply flow rate for medium alloys is 200 L / min, and the gas supply flow rate for high alloys is 200 L / min, with a gas supply time of 35–45 s.

[0040] 4) During the stage of impurity floating, the gas supply flow rate is 90-110 L / min and the gas supply time is 45-55 s;

[0041] 5) During the slag-blocking stage, the gas supply flow rate is 45-55 L / min, and the gas supply time is 45-55 s;

[0042] 6) During the post-blowing stage, the gas supply flow rate is 45-55 L / min and the gas supply time is 55-65 s.

[0043] Preferably, 1) at the beginning of the tapping stage, the gas supply flow rate is 50L / min and the gas supply time is 60s;

[0044] 2) During the deoxidizer and alloy addition stage, the gas supply flow rate for low alloys is 200L / min, the gas supply flow rate for medium alloys is 250L / min, and the gas supply flow rate for high alloys is 300L / min, with a gas supply time of 40s.

[0045] 3) During the slag-forming agent addition stage, the gas supply flow rate for low alloys is 150L / min, the gas supply flow rate for medium alloys is 200L / min, the gas supply flow rate for high alloys is 200L / min, and the gas supply time is 40s.

[0046] 4) During the stage of impurity floating, the gas supply flow rate is 100L / min and the gas supply time is 50s;

[0047] 5) During the slag-blocking stage, the gas supply flow rate is 50L / min and the gas supply time is 50s;

[0048] 6) During the post-blowing stage, the gas supply flow rate is 50L / min and the gas supply time is 60s.

[0049] Preferably, in the slag conditioning step, the slag composition is controlled according to the basicity of the steel slag, wherein the basicity of the slag is controlled between 2.0 and 2.5.

[0050] Preferably, the slag alkalinity is calculated according to the following formula:

[0051] Slag basicity = (slag weight × current CaO percentage + corresponding material-introduced CaO) / (slag weight × current SiO2 percentage + corresponding material-introduced SiO).

[0052] Preferably, slag-forming materials are used to regulate the basicity of the slag, and the slag-forming materials include lime, fluorite, calcium carbide, ferrosilicon, and calcium-barium silicon.

[0053] Preferably, the calcium feed rate for each furnace cycle is calculated according to the following formula:

[0054] Calcium wire feed rate per heat = steel tapping rate × (calcium content calculated by precise calcium treatment model - residual calcium content in steel) / (calcium content per unit calcium wire × calcium recovery rate).

[0055] Preferably, the precise calcium treatment model uses the reaction equilibrium line between Al-Ca and S-CA elements and the steel activity requirements of calcium aluminate products to calculate the required calcium content based on the actual steel composition.

[0056] This invention provides a control method for improving the castability of silicon-killed steel in irregularly shaped billets. By studying the factors affecting the castability of silicon-killed steel at various stages, this invention proposes a systematic, end-to-end control method that integrates various intelligent devices to establish an operational model. An intelligent argon blowing model is established at the converter endpoint, combined with dynamic deoxidation and alloying, and top lime and fluorite are used to rapidly form top slag with a certain alkalinity. At the refining station, an intelligent argon blowing system is used for rapid slag formation, and the slag composition is quickly analyzed using a LIBS online steel slag detection system to establish a slag control model, guiding the next step of slag adjustment. Calcium treatment in refining adopts graded control, with graded treatment based on different ladle conditions and process control situations. The recommended feed rate of nano-high-calcium wire is determined through full oxygen calculation, and a new seamless nano-high-calcium wire is used to ensure calcium yield. After calcium treatment, the intelligent argon blowing system is switched to soft blowing mode to ensure sufficient flotation of inclusions. In continuous casting, different top nozzle and slide block combinations are used according to different billet shapes to ensure the stability of the casting process.

[0057] The present invention has the following beneficial effects:

[0058] (1) Full-process control avoids the limitations of single-stage control.

[0059] (2) Various control models were designed, and the accuracy and stability of the control process were ensured through on-site intelligent and precise control.

[0060] (3) A dynamic control system was established, and appropriate control methods were selected for different furnace conditions, which avoided the rigidity of the control process and made the control process more effective and targeted.

[0061] (4) Through this invention, the cleanliness of silicon killed steel in special-shaped billets is greatly improved, the problem of nozzle nodules caused by poor cleanliness of steel is reduced, the castability of steel is greatly improved, the precise control of each link reduces material and energy consumption, reduces labor intensity, stabilizes the casting speed and output of continuous casting machine, and plays a positive role in reducing costs and increasing efficiency and production stability of the whole process. Detailed Implementation

[0062] This invention provides a method for controlling the castability of molten silicon killed steel in irregularly shaped billets, comprising the following steps:

[0063] A) After the smelting and blowing process is completed, a converter slag washing control model is established. Based on the carbon content at the end point and the carbon removal situation, the dynamic slag washing deoxidation regulations are compared to select deoxidation alloying and slag washing materials. The converter intelligent bottom blowing argon system is used to automatically adjust the bottom blowing intensity in conjunction with the charging sequence to ensure no alloy agglomeration and good slag washing effect.

[0064] The specific converter slag washing control model is shown in Table 1. This invention uses a 120-ton converter.

[0065] Table 1. Converter slag washing control model (based on the amount of feed per furnace)

[0066]

[0067] This invention combines converter tapping operations with intelligent argon blowing technology, adding alloys and slag-forming materials sequentially to promote rapid melting of alloys, deoxidizers, and slag washing agents, thereby improving alloy yield and slag formation rate. The bottom blowing intensity is set in six control stages according to the actual tapping time, with each stage adjusted differently based on the alloy content of the steel grade. In this invention, steel grades with an alloy content <1.2t are classified as low-alloy, those with an alloy content ≥1.2t and <2.0t as medium-alloy, and those with an alloy content ≥2.0t as high-alloy. Specific settings are shown in Table 2.

[0068] Table 2 Converter Alloy Quantity and Argon Blowing Flow Rate Settings

[0069]

[0070] Control Phase 1: This phase is at the beginning of tapping. There is less molten steel in the ladle. A large flow rate of gas supply can easily cause the temperature of the molten steel to drop, forming a crust on the surface of the permeable bricks. At this time, a small flow rate of gas supply is used, with the gas flow rate controlled at about 50L / min and the gas supply time being 60 seconds.

[0071] Control Phase 2: In this phase, alloys and deoxidizers are added. To prevent clumping during the addition of alloys and deoxidizers, a high flow rate control method is required. This facilitates the melting of alloys and deoxidizers, ensures uniform steel composition and temperature, and guarantees complete deoxidation. During this phase, the gas supply flow rate is controlled at approximately 200 L / min for low-alloy steels, approximately 250 L / min for medium-alloy steels, and approximately 300 L / min for high-alloy steels. The gas supply time is 40 seconds for all three phases.

[0072] Control Phase 3: At this stage, lime, synthetic slag, and other slag-forming agents are added to form top slag with a certain alkalinity, which helps to quickly form slag after refining. Excessive gas supply flow rate can easily cause slag entrapment, leading to an increase in inclusions such as CaO in the molten steel. Therefore, the gas supply flow rate needs to be appropriately reduced at this time. During this stage, the gas supply flow rate for low alloy steel grades is controlled at around 150 L / min, and the gas supply flow rate for medium and high alloy steel grades is controlled at around 200 L / min, with a gas supply time of 40 seconds for both.

[0073] Control Phase 4: In this phase, the deoxidizer, alloying agent, and slag-forming agent are basically melted. As the molten steel flows in, the deoxidation process leads to an increase in deoxidation products in the steel. At this point, an appropriate air supply flow rate is needed to quickly float the deoxidation products in the molten steel, improving the cleanliness of the steel and further homogenizing the composition and temperature of the molten steel. The air supply flow rate in this phase is controlled at approximately 100 L / min, with a supply time of 50 seconds.

[0074] Control Phase 5: This phase marks the later stage of steel discharge and the slag blocking phase. It is necessary to observe the steel flow and close the slide plate in time to prevent slag from falling. At this time, a small flow rate of air is required to prevent excessive flue gas from affecting the observation of the steel flow. The air supply flow rate is controlled at about 50L / min and the air supply time is 50 seconds.

[0075] Control Phase 6: After the steel is discharged in this phase, the post-blowing phase begins. The molten steel is ready to be hoisted away from the station. A small flow rate of air is used to further promote the floating of inclusions. The air flow rate in this phase is controlled at about 50L / min, and the air supply time is 60 seconds.

[0076] After all the above operations are completed, the ladle is taken out of the converter and sent to the LF refining process for processing. The refining process requires rapid slag formation. In this mode, the ladle liquid level fluctuates greatly and the steel slag liquid level interacts greatly, which promotes the deoxidation of slag. The refining argon blowing mode is the side blowing mode. In the side blowing mode, the argon flow rate is 400-500 L / min and the argon pressure is 1.0-1.8 MPa.

[0077] The refining process requires a stable ladle liquid level with minimal fluctuations, uniform composition and temperature, and promotion of inclusions to float. After stirring for 2 minutes, the argon mode is switched to the conventional mode, and an automatic temperature measuring robot is used to measure the temperature. Power is applied to promote slag formation and complete the initial slag formation. In the conventional mode, the argon flow rate is 100-200 L / min and the argon pressure is 0.4-0.6 MPa.

[0078] After initial slag formation, slag adjustment is carried out. The LIBS steel slag online detection system is used to take slag samples for online detection. The slag weight is calculated based on the slag thickness. After the steel slag composition is detected, a slag control model is established to calculate the amount of material to be added. The slag material is weighed and added according to the calculation data to accurately target the slag composition.

[0079] In this invention, the slag composition is controlled according to the basicity of the steel slag, and the basicity of the slag is controlled between 2.0 and 2.5, resulting in a high level of adsorption of inclusions.

[0080] The alkalinity of the slag is calculated according to the following formula:

[0081] Slag basicity = (slag weight × current CaO percentage + corresponding material-introduced CaO) / (slag weight × current SiO2 percentage + corresponding material-introduced SiO).

[0082] The slag basicity is controlled by using slag-forming materials, which include lime, fluorite, calcium carbide, ferrosilicon, and barium silicate. The lime contains 89% CaO, the main component of fluorite is CaFe2 with a Ca content of 80%, the calcium carbide contains 80% Ca, the ferrosilicon contains 74% Si, and the barium silicate contains 11% Ca and 52% Si.

[0083] Taking an addition of 100 kg / furnace as an example, the corresponding material input is calculated as follows:

[0084] Lime addition amount: 100kg / furnace, CaO introduced: 100*0.89=89kg

[0085] Calcium carbide addition: 100 kg / furnace, resulting in CaO addition of: 100 * 0.8 * 56 / 64 = 70 kg.

[0086] Fluorite addition: 100kg / furnace, resulting in the following CaO addition: 100*0.8*56 / 78=57kg.

[0087] Addition amount of silicon, calcium, and barium: 100 kg / furnace; CaO introduced: 100 * 0.11 * 56 / 40 = 15.4 kg; SiO2 introduced: 100 * 0.52 * 60 / 28 = 111 kg.

[0088] Ferrosilicon addition: 100kg / furnace, with SiO2 added: 100*0.74*60 / 28=158kg.

[0089] After refining, the required calcium content is calculated based on the total aluminum, sulfur, total oxygen, and residual calcium content in the molten steel using a precise calcium treatment calculation model. Combined with the calcium content of the calcium wire and the calcium yield, the calcium wire feeding amount is accurately calculated. This invention uses seamless nano-high-calcium wire for calcium treatment. After wire feeding, the argon blowing system is switched to soft blowing mode. In soft blowing mode, the argon flow rate is 50–100 L / min, and the argon pressure is 0.2–0.3 MPa. In soft blowing mode, the ladle surface moves slightly, preventing secondary oxidation of the molten steel while promoting the floating of inclusions.

[0090] The calcium feed rate for each furnace cycle is calculated according to the following formula:

[0091] Calcium wire feed rate per heat = molten steel quantity (calcium content calculated by precise calcium treatment model - residual calcium content in steel) / (calcium content per unit calcium wire × calcium recovery rate).

[0092] This invention uses seamless nano high-calcium wire, in which the calcium core reacts with the molten steel in the lower part of the ladle. Compared with ordinary high-calcium wire, which has large fluctuations in the liquid surface, serious steel spillage, large calcium loss and low calcium recovery rate (20%), seamless nano high-calcium wire has a smoother reaction in the molten steel, less calcium loss, avoids secondary gas absorption and oxidation of the molten steel, and has a high calcium recovery rate (32%).

[0093] After smelting, the combination of the sprue and slide block is designed according to the production section for casting. The sprue and slide block combination stabilizes the casting process. The specific combination is shown in Table 3.

[0094] Table 3 Combinations of Inlet and Slider

[0095] Section slider Sheung Shui Hau Speed ​​control range BB1 17.5, 18mm 23mm 0.9 m / min - 1.0 m / min BB2 17mm, 17.5mm 21mm 0.95m / min-1.05m / min BB3 18mm, 18.5mm 23mm 0.9 m / min - 1.0 m / min

[0096] The control method in this invention begins with a single heat of smelting. At the end of the smelting process, based on the TSO sample preparation, a suitable deoxidation slag washing model is selected. An intelligent argon blowing system is then used to control the argon blowing effect. After refining, the intelligent argon blowing system rapidly forms slag. Slag samples are taken and analyzed using the LIBS online steel slag detection system. The slag-forming model guides the next step of material feeding, and a dynamic calcium treatment model is established. The recommended feed rate of the nano-high-calcium wire is calculated using full oxygen. Combined with smelting conditions and ladle conditions, a new type of seamless nano-high-calcium wire is used for calcium treatment. In continuous casting, the combination of the top nozzle and slide block is determined according to different billet shapes. Through the intelligent equipment and control model of each process, the use of materials and the standardization of operations are standardized, avoiding the instability of the control process caused by manual operation and the limitations of single-stage control. This method has a good effect on improving the cleanliness of molten steel and the stability of process operation.

[0097] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a method for controlling the castability of molten silicon killed steel in shaped billets provided by the present invention, but it should not be construed as a limitation on the scope of protection of the present invention.

[0098] Example 1

[0099] 1. The steel grade for converter smelting is Q355B-1, with the internal code XG355B01, which is a high-alloy steel grade.

[0100] 2. After smelting, the carbon composition of the TSO sample is determined, and the amount of deoxidizer and top lime added is determined according to Table 1. The high alloy mode is selected for the converter tapping model, and the argon blowing flow rate is set according to Table 2. The deoxidizer, alloy and slag are added in sequence according to the order of the 6 control stages.

[0101] 3. The refining slag is introduced into the side-blowing mode for further stirring and slag formation. After stirring, argon gas is introduced into the normal mode, and power is applied to deoxidize the slag according to its condition. After initial slag formation, power is stopped, and the slag is monitored using the LIBS online detection system. The current slag composition is: CaO 48.36%, SiO2 25.39%, basicity 1.9, and slag weight 2t. The target slag basicity is controlled between 2 and 2.5. Based on the comprehensive calculation of slag addition, 180kg of lime, 75kg of fluorite, and 30kg of calcium carbide are added, with a target slag basicity of 2.34. The actual adjusted final slag composition is: CaO 52.83%, SiO2 21.93%, and basicity 2.40. The actual basicity of the refining slag differs from the predicted target basicity by 0.06, indicating that the slag basicity is precisely controlled.

[0102] 4. Based on the total oxygen calculation, the feed rate was 40m. The ladle was a normal ladle. The wire feed rate of 40m was entered into the wire feeding interface, and feeding began. After feeding was completed, the argon blowing system was switched to soft blowing mode. A sample from the continuous casting machine's tundish was taken, and the calcium content in the molten steel was found to be 14.6ppm, indicating that the calcium treatment effect in the molten steel was stably controlled.

[0103] 5. The continuous casting machine produces BB2 section using a 21mm top nozzle + (17+17.5) slide block combination.

[0104] 6. Samples were taken from the continuous casting machine crystallizer to measure the oxide inclusions in the molten steel. The total oxygen inclusion level in the steel was 39 ppm, indicating that the oxide inclusion level in the molten steel was effectively controlled.

[0105] Example 2

[0106] 1. The steel grade for converter smelting is Q235B-1, with the internal code XG235B01, which is a low-alloy steel grade.

[0107] 2. After smelting, prepare a carbon composition sample based on TSO. Determine the amount of deoxidizer and top lime to be added according to Table 1. Select the low alloy mode for the converter tapping model. Set the argon blowing flow rate according to Table 2. Add the deoxidizer, alloy, and slag in sequence according to the six control stages.

[0108] 3. The refining slag is fed into the station in a side-blowing mode for further stirring and slag formation. After stirring, argon gas is switched to a forward-blowing mode, and electricity is applied to deoxidize the slag according to its condition. After initial slag formation, the power is stopped, and the slag is monitored using an online LIBS system. The current slag composition is: CaO 58.25%, SiO2 22.11%, basicity 1.79, and slag weight 1.8t. The target slag basicity is controlled between 2 and 2.5. Based on the comprehensive calculation of the slag addition amount, 50kg of lime, 20kg of fluorite, and 60kg of silicon-calcium-barium are added, with a target slag basicity of 2.39. The actual adjusted final slag composition is: CaO 57.82%, SiO2 24.53%, and basicity 2.36. The actual basicity of the refining slag differs from the predicted target basicity by only 0.03, indicating precise control of the slag basicity.

[0109] 4. Based on the calculated total oxygen feed rate of 30m, and using a non-dedicated ladle, the feed rate was extended by 20m. The wire feed rate of 50m was entered into the wire feeding interface, and feeding began. After feeding, the argon blowing system was switched to soft blowing mode. A sample from the continuous casting machine's tundish was taken, and the calcium content in the molten steel was found to be 15.8ppm, indicating that the calcium treatment effect in the molten steel was stably controlled.

[0110] 5. The continuous casting machine produces section BB1 using a 23mm top nozzle + (18+17.5) slide block combination.

[0111] 6. Samples were taken from the continuous casting machine crystallizer to measure the oxide inclusions in the molten steel. The total oxygen inclusion level in the steel was 39 ppm, indicating that the oxide inclusion level in the molten steel was effectively controlled.

[0112] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the castability of molten silicon killed steel in irregularly shaped billets, comprising the following steps: A) After the smelting and blowing process is completed, a converter slag washing control model is established. Based on the carbon content and carbon removal at the end point, the type and amount of deoxidizer and slag washing materials are selected. The bottom blowing intensity is automatically adjusted by using the converter intelligent bottom blowing argon system in conjunction with the feeding sequence. The converter slag washing control model is as follows, based on the amount of feed per furnace: If the final carbon content is <0.04%, add 355~365 kg of silicon-calcium-barium, 60~65 kg of carbon powder, and 780~820 kg of top lime. The final carbon content is ≥0.04% and <0.06%. Add 335~345kg of silicon, calcium and barium, 45~50kg of carbon powder, and 680~720kg of top lime. The final carbon content is ≥0.06% and <0.08%. Add 295~305kg of silicon, calcium and barium, 30~35kg of carbon powder, and 580~720kg of top lime. The final carbon content is ≥0.08% and <0.10%. Add 275~285kg of silicon-calcium-barium, 15~20kg of carbon powder, and 480~520kg of top lime. The final carbon content is ≥0.10%. Add 245~255kg of silicon, calcium and barium, 0kg of carbon powder, and 430~470kg of top lime. The bottom blowing intensity is set according to the following 6 control stages based on the actual steel tapping time: 1) At the beginning of the tapping stage, the gas supply flow rate is 45~55L / min and the gas supply time is 55~65s; 2) During the deoxidizer and alloy addition stage, the gas supply flow rate is 190~310L / min, and the gas supply time is 35~45s; 3) During the slagging agent addition stage, the gas supply flow rate is 140~210L / min, and the gas supply time is 35~45s; 4) During the stage of impurity floating, the gas supply flow rate is 90~110L / min and the gas supply time is 45~55s; 5) During the slag-blocking stage, the gas supply flow rate is 45~55L / min, and the gas supply time is 45~55s; 6) During the post-blowing stage, the gas supply flow rate is 45~55L / min, and the gas supply time is 55~65s; B) Rapid slag formation: After tapping, the molten steel enters the LF refining process. The argon blowing system uses the side-blowing mode. After stirring for 2 minutes, the argon blowing system enters the normal mode and is powered on to promote slag formation, thus completing the initial slag formation. In the side-blowing mode, the argon flow rate is 400~500L / min and the argon pressure is 1.0~1.8Mpa; In the conventional mode, the argon flow rate is 100~200L / min and the argon pressure is 0.4~0.6Mpa; C) Slag adjustment: Use the LIBS steel slag online detection system to take slag samples for online detection. After the steel slag composition is detected, establish a slag control model. Based on the steel slag composition and slag material, the amount of deoxidizer added, calculate the final composition of the steel grade, and accurately predict and control the slag composition. D) Calcium treatment and soft blowing: After refining, establish a dynamic control model for calcium treatment, calculate the required calcium wire feed amount based on the total aluminum, sulfur, total oxygen and residual calcium content in the molten steel, and use seamless nano high-calcium wire for calcium treatment. After the wire feeding is completed, switch the argon blowing system to soft blowing mode. In the soft blowing mode, the argon flow rate is 50~100L / min and the argon pressure is 0.2~0.3Mpa; E) After smelting is completed, the combination of the top nozzle and slide block is designed according to the production section, and casting is carried out. When the cross-section is BB1, the slider is 17.5mm and 18mm, the inlet is 23mm, and the pulling speed is controlled at 0.9~1.0m / min; When the cross-section is BB2, the slider is 17mm and 17.5mm, the inlet is 21mm, and the pulling speed is controlled between 0.95 and 1.05m / min; When the cross-section is BB3, the slider is 18mm and 18.5mm, the inlet is 23mm, and the pulling speed is controlled at 0.9~1.0m / min.

2. The control method according to claim 1, characterized by, The converter slag washing control model is as follows, based on the amount of feed per furnace: If the final carbon content is <0.04%, add 360 kg of silicon-calcium-barium, 63-64 kg of carbon powder, and 800 kg of top lime. The final carbon content is ≥0.04% and <0.06%. Add 340kg of silicon-calcium-barium, 48~50kg of carbon powder, and 700kg of top lime. The final carbon content is ≥0.06% and <0.08%. Add 300kg of silicon, calcium and barium, 32~33kg of carbon powder, and 600kg of top lime. The final carbon content is ≥0.08% and <0.10%. Add 280kg of silicon, calcium and barium, 16~18kg of carbon powder, and 500kg of top lime. The final carbon content is ≥0.10%. Add 250 kg of silicon, calcium, and barium, 0 kg of carbon powder, and 450 kg of top lime.

3. The control method according to claim 2, characterized by, When the blowing process is completed but the temperature or composition does not meet the requirements, perform intermittent blowing, adding 30 kg of silicon, calcium and barium for every 100 m³ of intermittent blowing.

4. The control method according to claim 3, characterized by The argon bottom blowing flow rate is controlled according to the alloy content of the steel. Steel alloy content <1.2t is low alloy, steel alloy content ≥1.2t and <2.0t is medium alloy, and steel alloy content ≥2.0t is high alloy. 1) At the beginning of the tapping stage, the gas supply flow rate is 45~55L / min and the gas supply time is 55~65s; 2) During the deoxidizer and alloy addition stage, the gas supply flow rate for low alloys is 200 L / min, the gas supply flow rate for medium alloys is 250 L / min, and the gas supply flow rate for high alloys is 300 L / min, with a gas supply time of 35~45s. 3) During the slag-forming agent addition stage, the gas supply flow rate for low alloys is 150L / min, the gas supply flow rate for medium alloys is 200L / min, and the gas supply flow rate for high alloys is 200L / min, with a gas supply time of 35~45s. 4) During the stage of impurity floating, the gas supply flow rate is 90~110L / min and the gas supply time is 45~55s; 5) During the slag-blocking stage, the gas supply flow rate is 45~55L / min, and the gas supply time is 45~55s; 6) During the post-blowing stage, the gas supply flow rate is 45~55L / min and the gas supply time is 55~65s.

5. The control method according to claim 4, characterized by 1) At the beginning of the tapping stage, the gas supply flow rate is 50L / min and the gas supply time is 60s; 2) During the deoxidizer and alloy addition stage, the gas supply flow rate for low alloys is 200 L / min, the gas supply flow rate for medium alloys is 250 L / min, and the gas supply flow rate for high alloys is 300 L / min, with a gas supply time of 40 s. 3) During the slag-forming agent addition stage, the gas supply flow rate for low alloys is 150L / min, the gas supply flow rate for medium alloys is 200L / min, the gas supply flow rate for high alloys is 200L / min, and the gas supply time is 40s. 4) During the stage of impurity floating, the gas supply flow rate is 100L / min and the gas supply time is 50s; 5) During the slag-blocking stage, the gas supply flow rate is 50L / min and the gas supply time is 50s; 6) During the post-blowing stage, the gas supply flow rate is 50L / min and the gas supply time is 60s.

6. The control method according to claim 5, characterized by In the slag conditioning step, the slag composition is controlled according to the basicity of the steel slag, and the basicity of the slag is controlled between 2.0 and 2.

5.

7. The control method according to claim 6, characterized in that, The slag alkalinity is calculated according to the following formula: Slag basicity = (slag weight × current CaO percentage + corresponding material-introduced CaO) / (slag weight × current SiO2 percentage + corresponding material-introduced SiO).

8. The control method according to claim 7, characterized in that, The basicity of slag is controlled by using slag-forming materials, which include lime, fluorite, calcium carbide, ferrosilicon, and calcium-barium silicon.

9. The control method according to claim 8, characterized in that, The calcium feed rate for each furnace cycle is calculated using the following formula: Calcium wire feed rate per heat = steel tapping rate × (calcium content calculated by precise calcium treatment model - residual calcium content in steel) / (calcium content per unit of calcium wire × calcium recovery rate).

10. The control method according to claim 9, characterized in that, The precise calcium treatment model establishes the reaction equilibrium line between Al-Ca and S-CA elements and the activity requirements of molten steel for calcium aluminate products. The required calcium content is calculated based on the actual composition of the molten steel.

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