A method for shortening the waiting time of molten steel in a converter after stopping oxygen supply

Abstract

The application provides a method for shortening the waiting time of molten steel in the converter after the converter stops supplying oxygen, and the method comprises the following steps: establishing a precise control model of the converter end point phosphorus content under different smelting parameters, realizing the precise judgment of the converter end point phosphorus content, establishing a converter end point disposal model under the condition that the different difference values of the required phosphorus content of the steel grade and the converter end point phosphorus content after the converter stops supplying oxygen, adopting different end point control disposal modes for the heats with different difference values of the required phosphorus content of the steel grade and the converter end point phosphorus content after the converter stops supplying oxygen, and ensuring that the converter end point phosphorus content meets the standard and directly performs the steel tapping operation. The method can reduce the waiting time of the molten steel in the converter after the converter stops supplying oxygen, reduce the temperature drop of the converter during the steel tapping, improve the production efficiency, and reduce the erosion of the molten steel and the slag to the furnace lining.

Description

Technical Field

[0001] This invention belongs to the field of metal smelting technology, and in particular relates to a method for shortening the waiting time of molten steel in the furnace after oxygen supply to the converter is stopped. Background Technology

[0002] Converter steelmaking is a crucial technology in my country's steel production, playing an irreplaceable role in the industry. With the ongoing technological transformation and reforms, improving converter steelmaking technology is of paramount importance. In the actual steelmaking process, technical personnel must control the steelmaking endpoint and conduct thorough inspections, as this directly impacts the efficiency of the entire operation and the quality of the products.

[0003] Endpoint control in converter steelmaking refers to the control of various component parameters in the molten iron during the in-furnace hot metal treatment process. Endpoint control parameters include multiple aspects such as carbon content, phosphorus content, and sulfur content, and are important indicators affecting the quality of steel products and production costs.

[0004] Currently, after the TSO operation following the oxygen shutdown at the converter endpoint, the temperature, carbon, and oxygen content of the molten steel at the converter endpoint can be accurately determined. It is possible to quickly determine whether these parameters meet the requirements for tapping the steel grade produced by the converter. However, the phosphorus content in the molten steel needs to be determined by sampling and performing spectral or chemical analysis. Since the spectral or chemical analysis of the molten steel takes a long time, tapping cannot be carried out before the phosphorus content of the molten steel at the endpoint is determined (direct tapping is prone to quality problems such as scrap due to excessive phosphorus content). This results in a long residence time of the molten steel in the furnace after the oxygen shutdown at the converter endpoint, which has a significant impact on the temperature drop at the converter tapping and the improvement of production efficiency.

[0005] In addition, due to the strong oxidizing properties of molten steel and slag at the end of the converter, the prolonged residence of molten steel and slag in the furnace exacerbates the erosion of the furnace lining by molten steel and slag, which has a certain impact on the reduction of refractory material costs, the improvement of furnace lining quality, and the safe operation of the furnace. Summary of the Invention

[0006] The purpose of this invention is to provide a method for shortening the waiting time of molten steel in the converter after oxygen supply is stopped. This method establishes a precise control model for the final phosphorus content of the converter, accurately determining the final phosphorus content. It also establishes a model for handling different phosphorus content differences after oxygen supply is stopped. After oxygen supply is stopped, different final treatment methods are directly applied to heats with different phosphorus content differences, ensuring that the final phosphorus content meets the standard before tapping. This method reduces the waiting time of molten steel in the converter after oxygen supply is stopped, reduces the temperature drop at tapping, improves production efficiency, and slows down the erosion of the furnace lining by molten steel and slag.

[0007] This invention provides a method for shortening the waiting time of molten steel in a converter after oxygen supply is stopped, comprising the following steps:

[0008] A) After the converter is shut down, the dephosphorization coefficients of each process and the total phosphorus content of the raw materials for this furnace are determined based on the collected original parameters. The total dephosphorization coefficient for this furnace is determined by the dephosphorization coefficients of each process, and a precise control model for the phosphorus content at the converter endpoint is established based on the total phosphorus content of the raw materials for this furnace and the total dephosphorization coefficient for this furnace.

[0009] The original parameters include molten iron phosphorus content, molten iron silicon content, molten iron quantity, scrap steel phosphorus content, scrap steel quantity, first batch lime addition amount, slag removal time, initial carbon flame time, overflow time, process drying time, process lime addition amount, final temperature, influence value of final slag condition, and final carbon content.

[0010] The dephosphorization coefficients for the process include the dephosphorization coefficient based on the initial slag basicity, the dephosphorization coefficient based on the initial dephosphorization interval, the dephosphorization coefficient based on the initial slag stability, the dephosphorization coefficient based on the process slag basicity, the process phosphorus reversion coefficient, the dephosphorization coefficient based on the final temperature, the dephosphorization coefficient based on the final slag condition, and the dephosphorization coefficient based on the final oxidizing properties, which determine the overall dephosphorization coefficient for this furnace.

[0011] The final phosphorus content judgment value of this furnace converter = total phosphorus content of raw materials in this furnace - total phosphorus content of raw materials in this furnace × total dephosphorization coefficient of this furnace;

[0012] B) Determine the phosphorus content difference for this heat based on the phosphorus content requirement of the steel grade and the phosphorus content judgment value of the converter endpoint obtained in step A). ​​Establish an automatic judgment program for the difference between the converter endpoint phosphorus content judgment value and the phosphorus content requirement of the steel grade, and a converter endpoint treatment model after oxygen shutdown under different phosphorus content difference conditions. Based on the endpoint treatment model, determine whether to directly tap the steel in this heat or to tap the steel after endpoint adjustment based on the endpoint treatment model.

[0013] The difference in phosphorus content between this heat and the next heat = the required phosphorus content for the steel grade - the final phosphorus content judgment value at the end of this heat in the converter;

[0014] The following are the terminal treatment models for converters after oxygen shutdown under different phosphorus content differences:

[0015] If the phosphorus content difference is ≥0.003%, the steel can be directly tapped.

[0016] The phosphorus content difference is <0.003% and ≥0, and the steel is tapped after nitrogen blowing for 10 seconds;

[0017] If the phosphorus content difference is <0 and ≥-0.002%, add 1 kg / t of lime, blow oxygen for 10 seconds, and then tap the steel.

[0018] If the phosphorus content difference is <-0.002% and ≥-0.004%, add 2 kg / t of lime, blow oxygen for 15 seconds, and then tap the steel.

[0019] If the phosphorus content difference is <-0.004% and ≥-0.006%, add 3 kg / t of lime, blow oxygen for 20 seconds, and then tap the steel.

[0020] If the phosphorus content difference is less than -0.006%, a sample of molten steel is taken for analysis. After adjusting the molten steel composition, the phosphorus content of the molten steel is adjusted to meet the requirements for tapping before tapping.

[0021] Preferably, the dephosphorization coefficient of the initial slag basicity = converter dephosphorization base + (basicity of slag in this batch / basicity of converter slag smelting) × 10.

[0022] Preferably, the dephosphorization coefficient in the early dephosphorization interval is calculated as (initial carbon flame time of this furnace - slag formation time) / standard duration of early dephosphorization.

[0023] Preferably, the dephosphorization coefficient of the process slag basicity = 1 + process lime addition amount / (2.14 × iron silicon content × slag basicity required for process dephosphorization reaction / lime effective CaO content × iron amount) × 0.5.

[0024] Preferably, the dephosphorization coefficient of the initial slag stability is equal to the slag overflow time, wherein the slag overflow time is expressed in minutes.

[0025] Preferably, the process phosphorus reversion coefficient is equal to the process re-drying time, wherein the process re-drying time is expressed in minutes.

[0026] Preferably, the dephosphorization coefficient at the final temperature is 1 + (the standard value of the specified tapping temperature - the final temperature) × 0.02.

[0027] Preferably, the final slag condition dephosphorization coefficient = the final slag condition influence value.

[0028] Preferably, the endpoint oxidative dephosphorization coefficient = 1 + (0.1 - endpoint carbon content × 100) × 0.03.

[0029] Preferably, the total dephosphorization coefficient for this furnace is: (1 + dephosphorization coefficient of the initial slag basicity) × (1 + dephosphorization coefficient of the initial dephosphorization interval × 0.1) × (1 - dephosphorization coefficient of the initial slag stability × 0.01) × (1 + dephosphorization coefficient of the process slag basicity × 0.01) × (1 - dephosphorization coefficient of the process reversion × 0.01) × (1 + dephosphorization coefficient of the final temperature × 0.01) × (1 + dephosphorization coefficient of the final slag condition × 0.01) × (1 + dephosphorization coefficient of the final oxidative dephosphorization × 0.01).

[0030] This invention provides a method for shortening the waiting time of molten steel in the converter after oxygen supply is stopped, comprising the following steps: A) After oxygen supply is stopped in the converter, the dephosphorization coefficients of each process and the total phosphorus content of the raw materials for this heat are determined based on the collected original parameters. The total dephosphorization coefficient for this heat is determined by the dephosphorization coefficients of each process, and a precise control model for the final phosphorus content of the converter is established based on the total phosphorus content of the raw materials for this heat and the total dephosphorization coefficient for this heat; B) The phosphorus content difference for this heat is determined based on the phosphorus content required for the steel grade and the final phosphorus content judgment value of the converter obtained in step A). ​​An automatic judgment program for the difference between the final phosphorus content judgment value of the converter and the phosphorus content required for the steel grade is established, and a converter final treatment model after oxygen supply is stopped under different phosphorus content difference conditions is established. Based on the final treatment model, it is determined whether to directly tap the steel for this heat or to tap the steel after final adjustment based on the final treatment model. This application establishes a precise control model for the phosphorus content at the converter endpoint, accurately determining the phosphorus content at the converter endpoint. By establishing a model for the handling of converter endpoint issues after oxygen shutdown for different phosphorus content differences, different endpoint handling methods are adopted for heats with different phosphorus content differences, ensuring that steel is tapped only after the converter's final phosphorus content meets the standard. This method enables steel to be tapped directly in over 95% of heats without spectral or chemical analysis at the endpoint, reducing the waiting time of molten steel in the furnace after oxygen shutdown, minimizing converter temperature drop, improving production efficiency, and mitigating the erosion of the converter lining by molten steel and slag. This is of great significance for the enterprise's production safety and stability and for reducing process energy consumption. Detailed Implementation

[0031] This invention provides a method for shortening the waiting time of molten steel in the converter after oxygen supply is stopped, comprising the following steps:

[0032] A) After the converter is shut down, the dephosphorization coefficients of each process and the total phosphorus content of the raw materials for this furnace are determined based on the collected original parameters. The total dephosphorization coefficient for this furnace is determined by the dephosphorization coefficients of each process, and a precise control model for the phosphorus content at the converter endpoint is established based on the total phosphorus content of the raw materials for this furnace and the total dephosphorization coefficient for this furnace.

[0033] First, by collecting raw parameters, the dephosphorization coefficients for each process and the total phosphorus content of the raw materials for this batch are determined according to the following formulas and calculation methods.

[0034] The original parameters include molten iron phosphorus content, molten iron silicon content, molten iron quantity, scrap steel phosphorus content, scrap steel quantity, batch lime quantity, slag removal time, initial carbon flame time, overflow time, process drying time, process lime quantity, endpoint temperature, impact value of final slag condition, and endpoint carbon content.

[0035] The dephosphorization coefficients for the process include the dephosphorization coefficient based on the alkalinity of the slag in the early stage, the dephosphorization coefficient based on the dephosphorization interval in the early stage, the dephosphorization coefficient based on the stability of the slag in the early stage, the dephosphorization coefficient based on the alkalinity of the slag in the process, the phosphorus recovery coefficient in the process, the dephosphorization coefficient based on the final temperature, the dephosphorization coefficient based on the final slag condition, and the dephosphorization coefficient based on the final oxidizing properties, which determine the total dephosphorization coefficient for this furnace.

[0036] The relationship between the various dephosphorization coefficients and the original parameters in the process is shown in the following formula:

[0037] The dephosphorization coefficient of the slag in the early stage = converter dephosphorization base + (basicity of slag in this batch / basicity of converter slag smelting) × 10.

[0038] In this invention, the converter dephosphorization baseline is the dephosphorization rate data of each furnace batch statistically analyzed in production practice. The data is the average dephosphorization rate of furnace batches with a lower limit of 5% in actual converter production × 100.

[0039] The basicity of the slag in this batch refers to the basicity of the slag in the first batch of lime materials.

[0040] The basicity of converter slag refers to the lower limit of slag basicity required for the dephosphorization reaction during converter smelting, which is generally between 2.0 and 2.4. It is related to the FeO content of converter slag. When the FeO content of converter slag is high, the required basicity is low, and when the FeO content of converter slag is low, the required basicity is high.

[0041] Dephosphorization coefficient in the early stage of dephosphorization = (initial carbon flame time of this furnace - slag formation time) / standard duration of early stage dephosphorization.

[0042] In this invention, the standard duration for early dephosphorization refers to the average time from the initial melting of slag (initial slag formation) to the start of a large-scale carbon-oxygen reaction (initial carbon flame formation) during converter smelting. It is mainly related to the oxygen supply intensity of the converter, and the actual value used is based on production statistics.

[0043] The dephosphorization coefficient of slag basicity in the process = 1 + amount of lime added in the process / (2.14 × silicon content in molten iron × slag basicity required for dephosphorization reaction in the process / effective CaO content in lime × 10 × amount of molten iron) × 0.5.

[0044] In this invention, the slag basicity required for the dephosphorization reaction in the above-mentioned formula for calculating the slag basicity dephosphorization coefficient varies between steel plants, generally between 2.8 and 3.2. In the embodiment of this invention, it is 3. The effective CaO content of lime also varies between steel plants, generally between 0.78 and 0.9. In the embodiment of this invention, it is 0.8.

[0045] The dephosphorization coefficient of the initial slag stability is equal to the slag overflow time, which is expressed in minutes.

[0046] The process phosphorus reversion coefficient is equal to the process re-drying time, which is expressed in minutes.

[0047] The final temperature dephosphorization coefficient = 1 + (standard value of specified tapping temperature - final temperature) × 0.02. The standard value of specified tapping temperature in this invention is in °C and is mainly related to the steel grade and production process of the steel plant. It is generally between 1610 and 1660 °C, and is 1635 °C in the embodiment of this invention.

[0048] Dephosphorization coefficient of final slag condition = influence value of final slag condition.

[0049] The final oxidative dephosphorization coefficient = 1 + (0.1 - final carbon content × 100) × 0.03.

[0050] The dephosphorization coefficients for each process item are calculated using the above formulas. Then, the total dephosphorization coefficient for this batch is calculated using the following formula:

[0051] The total dephosphorization coefficient for this furnace run = (preliminary slag alkalinity dephosphorization coefficient × (1 + preliminary dephosphorization interval dephosphorization coefficient × 0.1) × (1 - preliminary slag stability dephosphorization coefficient × 0.01) × (1 + process slag alkalinity dephosphorization coefficient × 0.01) × (1 - process phosphorus reversion coefficient × 0.01) × (1 + final temperature dephosphorization coefficient × 0.01) × (1 + final slag condition dephosphorization coefficient × 0.01) × (1 + final oxidative dephosphorization coefficient × 0.01).

[0052] Meanwhile, based on the collected raw parameters, the total phosphorus content of the raw materials for this batch is calculated using the following formula:

[0053] Total phosphorus content of raw materials for this furnace = Phosphorus content of molten iron in this furnace × Quantity of molten iron + Phosphorus content of scrap steel in this furnace × Quantity of scrap steel.

[0054] The final phosphorus content judgment value for this converter cycle is calculated based on the following formula:

[0055] The final phosphorus content judgment value of this furnace converter is: total phosphorus content of raw materials in this furnace - total phosphorus content of raw materials in this furnace × total dephosphorization coefficient of this furnace.

[0056] After obtaining the final phosphorus content judgment value of the converter for this heat, the difference in phosphorus content for this heat is determined based on the required phosphorus content of the steel grade and the final phosphorus content judgment value of the converter for this heat. An automatic judgment program for the difference between the final phosphorus content judgment value of the converter and the required phosphorus content of the steel grade is established, as well as a converter final treatment model after oxygen shutdown under different phosphorus content difference conditions. Based on the final treatment model, it is determined whether to directly tap the steel for this heat or to tap the steel after adjusting the final treatment model.

[0057] The difference in phosphorus content between this heat and the next heat = the required phosphorus content for the steel grade - the final phosphorus content judgment value at the end of this heat in the converter;

[0058] The following are the terminal treatment models for converters after oxygen shutdown under different phosphorus content differences:

[0059] If the phosphorus content difference is ≥0.003%, the steel can be directly tapped.

[0060] The phosphorus content difference is <0.003% and ≥0, and the steel is tapped after nitrogen blowing for 10 seconds;

[0061] If the phosphorus content difference is <0 and ≥-0.002%, add 1 kg / t of lime, blow oxygen for 10 seconds, and then tap the steel.

[0062] If the phosphorus content difference is <-0.002% and ≥-0.004%, add 2 kg / t of lime, blow oxygen for 15 seconds, and then tap the steel.

[0063] If the phosphorus content difference is <-0.004% and ≥-0.006%, add 3 kg / t of lime, blow oxygen for 20 seconds, and then tap the steel.

[0064] If the phosphorus content difference is less than -0.006%, a sample of molten steel is taken for analysis. After adjusting the molten steel composition, the phosphorus content of the molten steel is adjusted to meet the requirements for tapping before tapping.

[0065] This application establishes a precise control model for the final phosphorus content of the converter under different smelting parameters, enabling accurate determination of the final phosphorus content. Furthermore, it establishes a model for handling the final phosphorus content after converter oxygen shutdown when the difference between the required phosphorus content for the steel grade and the final phosphorus content differs. Different endpoint control and handling methods are applied to heats where the difference between the required phosphorus content for the steel grade and the final phosphorus content differs after converter oxygen shutdown, ensuring that steel is tapped directly after the final phosphorus content meets the standard. This method reduces the waiting time of molten steel in the furnace after converter oxygen shutdown, reduces the temperature drop at tapping, improves production efficiency, and reduces the erosion of the furnace lining by molten steel and slag.

[0066] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a method for shortening the waiting time of molten steel in the furnace after oxygen supply is stopped, but this should not be construed as limiting the scope of protection of the present invention.

[0067] The calculation formulas for the following examples are as follows:

[0068] The dephosphorization coefficient of the slag in the early stage = converter dephosphorization base + (basicity of slag in this batch / basicity of converter slag smelting) × 10.

[0069] Dephosphorization coefficient in the early stage of dephosphorization = (initial carbon flame time of this furnace - slag formation time) / standard duration of early stage dephosphorization.

[0070] The dephosphorization coefficient of process slag basicity = 1 + process lime addition amount / (2.14 × iron silicon content × 3 / 0.8 × 10 × iron amount) × 0.5.

[0071] The dephosphorization coefficient of the initial slag stability is equal to the slag overflow time, which is expressed in minutes.

[0072] The process phosphorus reversion coefficient is equal to the process re-drying time, which is expressed in minutes.

[0073] The final temperature dephosphorization coefficient = 1 + (1635 - final temperature) × 0.02.

[0074] Dephosphorization coefficient of final slag condition = influence value of final slag condition.

[0075] The final oxidative dephosphorization coefficient = 1 + (0.1 - final carbon content × 100) × 0.03.

[0076] The total dephosphorization coefficient for this furnace run = (preliminary slag alkalinity dephosphorization coefficient × (1 + preliminary dephosphorization interval dephosphorization coefficient × 0.1) × (1 - preliminary slag stability dephosphorization coefficient × 0.01) × (1 + process slag alkalinity dephosphorization coefficient × 0.01) × (1 - process phosphorus reversion coefficient × 0.01) × (1 + final temperature dephosphorization coefficient × 0.01) × (1 + final slag condition dephosphorization coefficient × 0.01) × (1 + final oxidative dephosphorization coefficient × 0.01).

[0077] Total phosphorus content of raw materials for this furnace = Phosphorus content of molten iron in this furnace × Quantity of molten iron + Phosphorus content of scrap steel in this furnace × Quantity of scrap steel.

[0078] The final phosphorus content judgment value of this furnace converter is: total phosphorus content of raw materials in this furnace - total phosphorus content of raw materials in this furnace × total dephosphorization coefficient of this furnace.

[0079] Example 1

[0080] The method described in this application is used to control the tapping of steel after oxygen shutdown at the end of a 150t converter.

[0081] Heater 1: This heat was smelted as HRB400E-1. The steel grade required a phosphorus content of ≤0.030%. The amount of molten iron was 130t, with a silicon content of 0.35% and a phosphorus content of 0.130%. The amount of scrap steel was 30t, with a phosphorus content of 0.035%. 2600kg of lime was added to the batch. The slag removal time was 150 seconds after the start of oxygen supply. The initial carbon flame time was 350 seconds. The initial slag overflow time was 1 minute. 1000kg of lime was added during the process. The process drying time was 1 minute. The final slag was normal. The TSO temperature was 1650℃, and the carbon content was 0.10%. According to the formula above, the final phosphorus content judgment value of this heat was 0.0252%, and the phosphorus content difference was 0.0048%. The steel was tapped directly. The residence time of the molten steel in the furnace after the oxygen was stopped was 100 seconds. The temperature of the molten steel after tapping was 1595℃. The phosphorus content of the molten steel sample was 0.0270%.

[0082] Heater 2: This heat will smelt HRB400E-1 steel. The required phosphorus content for the tapped steel is ≤0.030%. The hot metal quantity is 130t, with a silicon content of 0.35% and a phosphorus content of 0.130%. The scrap steel quantity is 30t, with a phosphorus content of 0.035%. 2200kg of lime will be added per batch. Slag removal will occur 200 seconds after oxygen supply begins, the initial carbon flame will ignite 300 seconds later, and the initial slag overflow time will be 1 minute. 600kg of lime will be added during the process, and the drying time will be 2 minutes. After minutes, the final slag was normal. The TSO temperature was measured at 1660℃, and the carbon content was 0.12%. According to the formula above, the final phosphorus content of this heat was 0.0324%, and the phosphorus content difference was -0.0018%. 150 kg of lime was added according to the treatment plan, and oxygen was supplied again for 10 seconds before tapping. The residence time of the molten steel in the furnace after oxygen was stopped was 160 seconds. The temperature of the molten steel after tapping was 1603℃, and the phosphorus content of the molten steel sample was 0.0285%.

[0083] Heater 3: This heat smelted HRB400E-1 steel, with a phosphorus content of ≤0.030%, 130t of molten iron (0.35% silicon, 0.130% phosphorus), 30t of scrap steel (0.035% phosphorus), and 2200kg of lime added per batch. Slag removal occurred 200 seconds after oxygen supply began, the initial carbon flame ignition occurred 250 seconds later, and the initial slag overflow time was 2 minutes. 800kg of lime was added during the process, and the drying time was 5 minutes. The final slag difference was [not specified]. The TSO-measured temperature was 1660℃, and the carbon content [not specified]. The amount was 0.12%. According to the formula above, the final phosphorus content of this heat was 0.038%, and the difference in phosphorus content was -0.008%. According to the treatment plan, the phosphorus content of the molten steel sample was analyzed by spectral analysis and found to be 0.0378%. 600 kg of lime was added, and oxygen was supplied again for 40 seconds. The phosphorus content of the sample was analyzed by spectral analysis again and found to be 0.0280%. The steel tapping operation was carried out. The residence time of the molten steel in the furnace from the oxygen shutdown to the tapping was 340 seconds. After the steel tapping was completed, the temperature of the molten steel was measured at 1597℃, and the phosphorus content of the molten steel sample was 0.0295%.

[0084] By shortening the waiting time of molten steel in the furnace after the oxygen supply to the converter is stopped, the steel tapping after the oxygen supply to the converter was controlled in 100 heats. 85 heats were tapped directly, and 13 heats were tapped directly after treatment. After taking molten steel samples for analysis, the phosphorus content of the molten steel was treated according to the steel composition and then tapped for 2 more heats. The average residence time of molten steel in the furnace from the oxygen supply to tapping in 100 heats was 112.6 seconds, and the average temperature drop at tapping was 55.24℃.

[0085] Comparative Example 1

[0086] Using existing methods to control steel tapping after oxygen shutdown at the end of a 150t converter.

[0087] Heater 1: This heat was smelted as HRB400E-1. The phosphorus content of the steel was ≤0.030%. The amount of molten iron was 130t, the silicon content of the molten iron was 0.35%, the phosphorus content of the molten iron was 0.130%, the amount of scrap steel was 30t, and the phosphorus content of the scrap steel was 0.035%. 2600kg of lime was added to the batch. The slag removal time was 150 seconds after the oxygen supply started, the initial carbon flame time was 350 seconds, the initial slag overflow time was 1 minute, 1000kg of lime was added during the process, the process drying time was 1 minute, and the final slag was normal. The TSO temperature was 1650℃, the carbon content was 0.10%, and the phosphorus content of the molten steel sample was 0.0252%. The steel was tapped directly. The residence time of the molten steel in the furnace after the oxygen was stopped was 180 seconds. The temperature of the molten steel after tapping was 1593℃, and the phosphorus content of the molten steel sample was 0.0270%.

[0088] Heater 2: This heat will smelt HRB400E-1 steel. The phosphorus content of the steel will be ≤0.030%. The amount of molten iron is 130t, the silicon content of the molten iron is 0.35%, the phosphorus content of the molten iron is 0.130%, the amount of scrap steel is 30t, and the phosphorus content of the scrap steel is 0.035%. 2200kg of lime will be added to each batch of material. The slag removal time is 200 seconds after the start of oxygen supply, the initial carbon flame time is 300 seconds, the initial slag overflow time is 1 minute, and 600kg of lime will be added during the process. The process drying time was 2 minutes, the final slag was normal, the TSO temperature was 1660℃, the carbon content was 0.12%, and the phosphorus content of the molten steel sample was 0.0324% according to spectral analysis. After adding 150 kg of lime and supplying oxygen again for 10 seconds, the phosphorus content of the molten steel sample was 0.027% and then tapped. The residence time of the molten steel in the furnace after oxygen was stopped and tapped was 310 seconds. After tapping, the temperature of the molten steel was measured at 1598℃, and the phosphorus content of the molten steel sample was 0.0285%.

[0089] Heater 3: This heat will smelt HRB400E-1 steel. The phosphorus content of the steel will be ≤0.030%. The amount of molten iron is 130t, with a silicon content of 0.35% and a phosphorus content of 0.130%. The amount of scrap steel is 30t, with a phosphorus content of 0.035%. 2200kg of lime will be added to the batch. The slag removal time is 200 seconds after the start of oxygen supply, the initial carbon flame time is 250 seconds, and the initial slag overflow time is 2 minutes. 800kg of lime will be added during the process. The drying time was 5 minutes, the final slag difference was small, the TSO temperature was 1660℃, the carbon content was 0.12%, and the phosphorus content of the molten steel sample was 0.038% according to spectral analysis. After adding 600 kg of lime and supplying oxygen again for 40 seconds, the phosphorus content of the sample was 0.0280%. The steel tapping operation was then carried out. The residence time of the molten steel in the furnace after the oxygen was stopped was 340 seconds. After tapping, the temperature of the molten steel was 1597℃, and the phosphorus content of the molten steel sample was 0.0295%.

[0090] Using existing methods, after the converter oxygen was shut off at the end point, the steel was tapped in 100 heats. Sampling analysis showed that the phosphorus content met the standard and the steel was tapped directly in 85 heats. After sampling analysis showed that the phosphorus content exceeded the standard, the steel was treated and sampled again in 15 heats. The average waiting time from the converter oxygen shutdown to the tapping in 100 heats was 200.1 seconds, and the average temperature drop at tapping was 57.77℃.

[0091] The residence time of molten steel in the furnace from the time the oxygen was stopped to the tapping temperature drop in the examples and comparative examples are compared. The results are shown in Table 1.

[0092] Table 1 Comparison of Material Consumption and Cost

[0093] Example 1 112.6 55.24 Comparative Example 1 200.1 57.77 Comparison of Example 1 and Comparative Example 1 -87.5 -2.53

[0094] As shown in Table 1, the method of this application can reduce the waiting time of molten steel in the furnace after the converter oxygen is shut down, reduce the temperature drop when the steel is tapped from the converter, improve production efficiency, and reduce the erosion of the furnace lining by molten steel and slag.

[0095] 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 shortening the waiting time of molten steel in a converter after oxygen supply is stopped, comprising the following steps: A) After the converter stops oxygen production, determine the dephosphorization coefficients of each process and the total phosphorus content of the raw materials for this batch based on the collected raw parameters. Determine the total dephosphorization coefficient for this batch based on the dephosphorization coefficients of each process, and establish a precise control model for the phosphorus content at the converter endpoint based on the total phosphorus content of the raw materials for this batch and the total dephosphorization coefficient for this batch. The original parameters include molten iron phosphorus content, molten iron silicon content, molten iron quantity, scrap steel phosphorus content, scrap steel quantity, first batch lime input quantity, slag removal time, initial carbon flame time, overflow time, process drying time, process lime input quantity, final temperature, influence value of final slag condition, and final carbon content. The dephosphorization coefficients for the process include the dephosphorization coefficient based on the initial slag basicity, the dephosphorization coefficient based on the initial dephosphorization interval, the dephosphorization coefficient based on the initial slag stability, the dephosphorization coefficient based on the process slag basicity, the process phosphorus reversion coefficient, the dephosphorization coefficient based on the final temperature, the dephosphorization coefficient based on the final slag condition, and the dephosphorization coefficient based on the final oxidizing properties, which determine the overall dephosphorization coefficient for this furnace. The dephosphorization coefficient of the slag basicity in the early stage = converter dephosphorization base + (basicity of slag in this batch / basicity of converter slag smelting) × 10; Dephosphorization coefficient in the early stage of dephosphorization = (initial carbon flame time of this furnace - slag removal time) / standard duration of early stage dephosphorization; The dephosphorization coefficient of slag basicity in the process = 1 + amount of lime added in the process / (2.14 × silicon content in molten iron × slag basicity required for dephosphorization reaction in the process / effective CaO content in lime × 10 × amount of molten iron) × 0.5; The dephosphorization coefficient of the initial slag stability is equal to the slag overflow time, which is expressed in minutes. Process phosphorus recovery coefficient = process re-drying time, wherein the process re-drying time is expressed in minutes; The final temperature dephosphorization coefficient = 1 + (standard value of specified tapping temperature - final temperature) × 0.02; Dephosphorization coefficient of final slag condition = Influence value of final slag condition; The final oxidative dephosphorization coefficient = 1 + (0.1 - final carbon content × 100) × 0.03; The total dephosphorization coefficient for this furnace run = (Preliminary slag basicity dephosphorization coefficient × (1 + Preliminary dephosphorization interval dephosphorization coefficient × 0.1) × (1 - Preliminary slag stability dephosphorization coefficient × 0.01) × (1 + Process slag basicity dephosphorization coefficient × 0.01) × (1 - Process phosphorus reversion coefficient × 0.01) × (1 + Final temperature dephosphorization coefficient × 0.01) × (1 + Final slag condition dephosphorization coefficient × 0.01) × (1 + Final oxidative dephosphorization coefficient × 0.01); The final phosphorus content judgment value of this furnace converter is: the total phosphorus content of the raw materials in this furnace - the total phosphorus content of the raw materials in this furnace × the total dephosphorization coefficient of this furnace; B) Determine the phosphorus content difference for this heat based on the phosphorus content requirement of the steel grade and the phosphorus content judgment value at the converter endpoint obtained in step A). ​​Establish an automatic judgment program for the difference between the phosphorus content judgment value at the converter endpoint and the phosphorus content requirement of the steel grade, and a converter endpoint treatment model after oxygen shutdown under different phosphorus content difference conditions. Based on the endpoint treatment model, determine whether to directly tap the steel in this heat or to tap the steel after endpoint adjustment based on the endpoint treatment model. The difference in phosphorus content between this heat and the next heat = the required phosphorus content for the steel grade - the final phosphorus content judgment value at the end of this heat in the converter; The following are the terminal treatment models for converters after oxygen shutdown under different phosphorus content differences: If the phosphorus content difference is ≥0.003%, the steel can be directly tapped. The phosphorus content difference is <0.003% and ≥0, and the steel is tapped after nitrogen blowing for 10 seconds; If the phosphorus content difference is <0 and ≥-0.002%, add 1 kg / t of lime, blow oxygen for 10 seconds, and then tap the steel. If the phosphorus content difference is <-0.002% and ≥-0.004%, add 2 kg / t of lime, blow oxygen for 15 seconds, and then tap the steel. If the phosphorus content difference is <-0.004% and ≥-0.006%, add 3 kg / t of lime, blow oxygen for 20 seconds, and then tap the steel. If the phosphorus content difference is less than -0.006%, a sample of molten steel is taken for analysis. After adjusting the molten steel composition, the phosphorus content of the molten steel is adjusted to meet the requirements for tapping before tapping.