Dephosphorization treatment method for converter

Abstract

The invention provides a dephosphorization treatment method of a converter, which comprises the following steps: if the phosphorus content standard exceeding value of the converter end point molten steel is less than or equal to 0.005%, the end point temperature is greater than or equal to 1640 DEG C, and the end point carbon content is less than or equal to 0.07%, obtaining aluminum killed steel large ladle casting residual molten steel and attached refining slag, and pouring into a steel ladle to obtain refined hot slag; pouring out terminal slag in the converter according to a preset slag pouring amount; the refined hot-state slag is poured into the converter, and after the converter returns to the zero position, furnace slag in the converter is purged through a nitrogen purging gun; and after a first preset time, adjusting the bottom blowing mode of the converter into a strong stirring mode, and after standing for a second preset time, carrying out a tapping process, so as to solve the problems that steel consumption is increased, furnace lining erosion is aggravated, the alloy yield is reduced, the production cost is reduced and the like due to the fact that the oxygen content in molten steel and the iron oxide content in slag are obviously increased in a current converter dephosphorization treatment method. And the quality of the molten steel is influenced by the peroxidation of the molten steel.

Description

Technical Field

[0001] This application relates to the field of steelmaking process technology, and in particular to a dephosphorization treatment method for a converter. Background Technology

[0002] In converter steelmaking, dephosphorization is a crucial task, directly affecting the quality of molten steel and its ability to meet the production requirements of different steel grades. This is especially true for low-phosphorus steel production, where the control of phosphorus content in the molten steel is extremely stringent. However, in actual production, due to a combination of factors such as fluctuations in molten iron composition, difficulties in achieving ideal slag-forming conditions, deviations in temperature control, and improper process operation, the phosphorus content in the molten steel at the blowing endpoint often exceeds the target requirement, resulting in a high-phosphorus finish.

[0003] To address the issue of high phosphorus levels at the end of converter blowing, a common method is to perform "supplementary blowing." Specifically, after high phosphorus levels are detected, the converter receives a second oxygen supply, while slag-forming materials such as lime and ore are added to the furnace. This secondary oxygen supply provides a stronger oxidizing environment, and the added slag-forming materials further promote the dephosphorization reaction, thereby reducing the phosphorus content in the molten steel.

[0004] Although the "re-blowing" treatment method can reduce the phosphorus content of molten steel to some extent, it has several significant drawbacks. Firstly, the "re-blowing" operation significantly increases the oxygen content in the molten steel and the iron oxide content in the slag. This not only leads to a substantial increase in steel feedstock consumption and production costs but also exacerbates furnace lining erosion and shortens converter lifespan. Simultaneously, excessively high oxygen content reduces alloy yield and easily triggers steel over-oxidation, thus adversely affecting steel quality, such as reducing toughness and plasticity. Secondly, when the final carbon content is low, the "re-blowing" method is extremely difficult to implement, easily resulting in excessive steel composition, further impacting normal production and the stability of steel quality. Summary of the Invention

[0005] This application provides a dephosphorization treatment method for converters to solve the technical problems of existing converter dephosphorization treatment methods, which significantly increase the oxygen content in molten steel and the iron oxide content in slag, leading to increased steel material consumption, intensified furnace lining erosion, reduced alloy yield, and easy initiation of steel over-oxidation, affecting steel quality; and the difficulty of treatment when the final carbon is too low, which easily leads to excessive composition.

[0006] This application provides a dephosphorization treatment method for a converter, including: If the phosphorus content of the final molten steel in the converter exceeds the standard by less than or equal to 0.005%, the final temperature is greater than or equal to 1640°C, and the final carbon content is less than or equal to 0.07%, then the remaining molten steel and the attached refining slag in the aluminum-killed steel ladle are obtained and poured into the ladle to obtain the refining hot slag. The final slag in the converter is poured out according to the preset slag amount; The hot refined slag is poured into the converter. After the converter returns to the 0 position, the slag inside the converter is purged with a nitrogen purging gun. After the first preset time, the bottom blowing mode of the converter is adjusted to the strong stirring mode, and after the second preset time, the steel tapping process is carried out.

[0007] In some embodiments, the method further includes: If the phosphorus content of the molten steel at the converter endpoint exceeds the standard by less than or equal to 0.005%, the endpoint temperature is greater than or equal to 1620°C, and the endpoint carbon content is less than or equal to 0.05%, then the remaining molten steel and the attached refining slag in the aluminum-killed steel ladle are obtained and poured into the ladle to obtain the refining hot slag.

[0008] In some embodiments, the basicity of the refined hot slag is greater than or equal to 4, and the Al2O3 content of the refined hot slag is greater than or equal to 20%.

[0009] In some embodiments, the preset slag dumping amount is in the range of one-half to three-quarters of the total slag amount at the end point in the converter.

[0010] In some embodiments, the position of the nitrogen purging gun is in the range of 1500mm to 1600mm.

[0011] In some embodiments, the nitrogen pressure of the nitrogen purging gun is in the range of 0.85 MPa to 0.95 MPa.

[0012] In some embodiments, the first preset time is in the range of 30s to 50s.

[0013] In some embodiments, the bottom-blowing intensity of the strong stirring mode is 5.54 Nm. 3 / (t·h).

[0014] In some embodiments, the second preset time is in the range of 1 min to 2 min.

[0015] In some embodiments, the step of adjusting the bottom blowing mode of the converter to a strong stirring mode after a first preset time, and then allowing it to stand for a second preset time before proceeding with the steel tapping process includes: After the first preset time, the bottom blowing mode of the converter is adjusted to the strong stirring mode. After the second preset time, a sample is taken from the converter to determine the phosphorus content. If the phosphorus content is within the acceptable range, the steel tapping process will proceed.

[0016] This application provides a dephosphorization treatment method for a converter, comprising: if the phosphorus content of the final molten steel in the converter exceeds the standard by less than or equal to 0.005%, the final temperature is greater than or equal to 1640°C, and the final carbon content is less than or equal to 0.07%, then obtaining the remaining molten steel and attached refining slag in the aluminum-killed steel ladle and pouring it into the ladle to obtain refined hot slag; pouring out the final slag in the converter according to a preset slag pouring amount; pouring the refined hot slag into the converter, and waiting for the converter to return to the 0 position, The slag inside the converter is purged with a nitrogen purging gun. After a first preset time, the bottom blowing mode of the converter is adjusted to a strong stirring mode. After a second preset time, the steel tapping process is carried out. This method addresses the problem that current converter dephosphorization treatment methods significantly increase the oxygen content in the molten steel and the iron oxide content in the slag, leading to increased steel material consumption, intensified furnace lining erosion, reduced alloy yield, and easy occurrence of steel over-oxidation, affecting steel quality. Furthermore, it is difficult to process when the final carbon content is too low, and the composition may exceed the standard. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the dephosphorization treatment method for the converter in this application. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0020] In some technologies, converter dephosphorization significantly increases the oxygen content in molten steel and the iron oxide content in slag, leading to increased steel consumption, intensified furnace lining erosion, reduced alloy yield, and a higher risk of steel over-oxidation, thus affecting steel quality. Furthermore, when the final carbon level is low, treatment becomes difficult, and excessive component levels are likely to occur. To address these technical problems, this application provides a converter dephosphorization method, which is described below: like Figure 1 The diagram shown is a flowchart of the dephosphorization treatment method for the converter in this application.

[0021] This application provides a dephosphorization treatment method for a converter, comprising the following steps: S100: If the phosphorus content of the final molten steel in the converter exceeds the standard by less than or equal to 0.005%, the final temperature is greater than or equal to 1640°C, and the final carbon content is less than or equal to 0.07%, then the remaining molten steel and the attached refining slag in the aluminum-killed steel ladle are obtained and poured into the ladle to obtain the refining hot slag; the basicity of the refining hot slag is greater than or equal to 4, and the Al2O3 content of the refining hot slag is greater than or equal to 20%.

[0022] S110: If the phosphorus content of the final molten steel in the converter exceeds the standard by less than or equal to 0.005%, the final temperature is greater than or equal to 1620°C, and the final carbon content is less than or equal to 0.05%, then the remaining molten steel and the attached refining slag in the aluminum-killed steel ladle are obtained and poured into the ladle to obtain the refining hot slag.

[0023] S200: The final slag in the converter is poured out according to a preset slag amount; the preset slag amount is in the range of one-half to three-quarters of the total amount of final slag in the converter.

[0024] S300: The hot refined slag is poured into the converter. After the converter returns to the 0 position, the slag inside the converter is purged with a nitrogen purging gun. The position of the nitrogen purging gun is between 1500mm and 1600mm. The nitrogen pressure of the nitrogen purging gun is between 0.85MPa and 0.95MPa.

[0025] S400: After the first preset time, the bottom blowing mode of the converter is adjusted to the strong stirring mode. After a second preset time, the steel tapping process begins. The first preset time is within the range of 30s to 50s. The bottom blowing intensity of the strong stirring mode is 5.54 Nm. 3 / (t·h). The second preset time is within the range of 1 min to 2 min.

[0026] The steps of adjusting the bottom blowing mode of the converter to the strong stirring mode after the first preset time, and then allowing it to stand for a second preset time before proceeding with the steel tapping process include the following steps: S410: After the first preset time, adjust the bottom blowing mode of the converter to the strong stirring mode, and after the second preset time, take a sample from the converter to determine the phosphorus content.

[0027] S420: If the phosphorus content is within the acceptable range, proceed with the steel tapping process.

[0028] This application provides a dephosphorization treatment method for a converter, the specific steps of which are as follows: Step 1: Endpoint Determination This method applies when the phosphorus content of the molten steel at the converter endpoint exceeds the standard, and the excess value of the phosphorus content at the endpoint is ≤0.005%, and one of the following conditions is met.

[0029] (1) The endpoint temperature is ≥1640°C and the endpoint carbon content is ≤0.07%.

[0030] (2) The endpoint temperature is ≥1620°C and the endpoint carbon content is ≤0.05%.

[0031] The above steps allow for precise selection of applicable scenarios: targeting only conditions with slight phosphorus exceedances and where furnace temperature and carbon content meet requirements, ensuring the effectiveness of subsequent operations. High-temperature, low-carbon conditions are beneficial to the reaction kinetics of slag and molten steel, improving dephosphorization efficiency. Ineffective operations are avoided: if phosphorus exceedances are severe or furnace conditions are unsuitable (e.g., low temperature, high carbon), other methods (e.g., supplementary blowing) must be used to prevent resource waste.

[0032] Step 2: Collection and preparation of hot refining slag Collect the remaining molten steel and adhering refining slag from 2 to 3 heats of aluminum-killed steel ladle, and pour them into a single ladle for later use. The collected hot refining slag must meet the following requirements: basicity R ≥ 4.0, Al2O3 ≥ 20%.

[0033] The above steps provide a highly active dephosphorization medium: aluminum-killed steel refining slag is rich in high-basicity oxides (such as CaO) and Al2O3, which can quickly react with phosphorus in molten steel to form stable phosphates that enter the slag phase. Resource recycling: The waste slag generated from secondary refining is converted into dephosphorization raw materials, reducing solid waste emissions and lowering treatment costs.

[0034] Furthermore, the synergistic effect of alkalinity and Al2O3: high alkalinity (R≥4.0) promotes the increase of phosphorus distribution ratio (Lp), and Al2O3 can stabilize the slag structure and avoid the decrease in slag viscosity due to excessive low melting point phases, which would affect the dephosphorization effect.

[0035] Step 3: Pour out the slag After determining that the conditions are met, most of the final slag in the converter is poured out, with the amount of slag poured out being 1 / 2 to 3 / 4 of the total slag.

[0036] The above steps can be used to remove low-activity slag: the original slag has a reduced iron oxide (FeO) content due to prolonged blowing, resulting in decreased dephosphorization capacity. After slag removal, reaction space is created for the high-activity refining slag. Slag quantity control: retaining some of the original slag helps maintain the furnace temperature and prevents a sudden drop in steel temperature due to excessive slag removal.

[0037] Step 4: Pour the refined hot slag prepared in Step 2 into the converter.

[0038] After restoring the converter to the "0" position, nitrogen is used to purge the slag inside the furnace. The lance position is 1500-1600mm, the nitrogen pressure is 0.85-0.95MPa, and the lance is lifted after purging nitrogen for 30-50 seconds.

[0039] The above steps ensure uniform slag mixing: nitrogen purging, through physical stirring, thoroughly mixes the newly added refining slag with the residual slag, forming a uniform, high-alkalinity reaction medium. It also removes inclusions: purging promotes the flotation of non-metallic inclusions in the molten steel, reducing their interference with the dephosphorization reaction. Finally, it optimizes the reaction interface: lance position and pressure control ensure that the purging range covers the entire furnace space, avoiding localized dead zones.

[0040] Step 5: Switch the bottom blowing mode to strong stirring mode, and set the bottom blowing intensity to 5.54 Nm. 3 / (t·h), let stand for 1 to 2 minutes.

[0041] The above steps enhance molten pool stirring: strong stirring promotes interface renewal between molten steel and slag, accelerates the mass transfer of phosphorus from molten steel to slag, and increases the dephosphorization rate. Controlling the reaction temperature: the settling stage allows the dephosphorization reaction to proceed fully while avoiding excessive stirring that could cause the molten steel temperature to drop too quickly. Kinetic optimization: 5.54 Nm 3 The bottom blowing intensity of / (t·h) has been optimized to reduce the erosion of the furnace lining by gas while ensuring the stirring effect.

[0042] Step 6: Tapping the steel After the settling process, sampling and analysis confirm that the phosphorus content is within acceptable limits, and the steel can be tapped normally.

[0043] Quality control: Phosphorus content is confirmed to meet standards through sampling to ensure that the molten steel meets the requirements of subsequent processes. Production continuity: Rapid tapping of steel avoids excessive drop in furnace temperature and maintains production rhythm.

[0044] This application provides a dephosphorization treatment method for a converter, which has the following implementation methods: 1. Endpoint determination This method applies when the phosphorus content of the molten steel at the converter endpoint exceeds the standard, and the excess value of the phosphorus content at the endpoint is ≤0.005%, and one of the following conditions is met.

[0045] (1) The endpoint temperature is ≥1640°C and the endpoint carbon content is ≤0.07%.

[0046] (2) The endpoint temperature is ≥1620°C and the endpoint carbon content is ≤0.05%.

[0047] The required final phosphorus content and the final conditions of the converters in Examples 1-3 are shown in Table 1.

[0048] Table 1: Statistical Table of Required Phosphorus Content and Converter End-Point Results for Examples 1-3

[0049] 2. Collection and preparation of hot refining slag Collect the remaining molten steel and adhering refining slag from 2 to 3 heats of aluminum-killed steel ladle, and pour them into a single ladle for later use. The collected hot refining slag must meet the following requirements: basicity R ≥ 4.0, Al₂O₃ ≥ 20%. See Table 2 for the refining slag collection details of Examples 1-3.

[0050] Table 2: Statistics on the Collection of Refining Slag in Examples 1-3

[0051] 3. Discarding the slag Most of the final slag in the converter is poured out, with the amount of slag poured out being 1 / 2 to 3 / 4 of the total slag.

[0052] 4. Pour the refined hot slag prepared in step 2 into the converter.

[0053] After restoring the converter to the "0" position, nitrogen was used to purge the slag inside the furnace. The lance position was 1500-1600mm, the nitrogen pressure was 0.85-0.95MPa, and the lance was lifted after purging nitrogen for 30-50 seconds. The specific nitrogen purging parameters for Examples 1-3 are shown in Table 3.

[0054] Table 3: Statistical Table of Nitrogen Purging Parameters for Examples 1-3

[0055] 5. Switch the bottom blowing mode to strong stirring mode, and set the bottom blowing intensity to 5.54 Nm. 3 / (t·h), let stand for 1 to 2 minutes. The standing times for Examples 1-3 were 1.5 minutes, 1.8 minutes, and 2.0 minutes, respectively.

[0056] 6. Steel tapping After the settling treatment, sampling and analysis confirmed that the phosphorus content was within acceptable limits, and the steel could then be tapped normally. The phosphorus content after settling treatment in Examples 1-3 is shown in Table 4.

[0057] Table 4: Statistical table of phosphorus content after static treatment in Examples 1-3

[0058] Ultimately, the phosphorus content of the treated samples from Examples 1-3 all met the requirements for steelmaking.

[0059] This application provides a dephosphorization treatment method for a converter, which has the following beneficial effects: (1) Low cost and few side effects. It avoids the current "re-blowing" operation, thereby reducing the iron loss, increased alloy consumption and severe furnace lining erosion caused by it. At the same time, it prevents the strong over-oxidation of molten steel caused by "re-blowing", which is conducive to improving alloy yield and molten steel purity.

[0060] (2) Stable and controllable processing. The reaction environment is regulated by replacing the slag and strong stirring is used to promote the reaction. The dephosphorization process is stable and has little impact on the temperature and oxygen content of the molten steel, making it easy to control.

[0061] (3) Resource reuse. The hot, high-basicity slag produced by the secondary refining of molten steel was utilized, realizing the resource utilization of solid waste.

[0062] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the embodiments of this application. It should be understood that the above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solutions of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. A dephosphorization treatment method for a converter, characterized in that, include: If the phosphorus content of the final molten steel in the converter exceeds the standard by less than or equal to 0.005%, the final temperature is greater than or equal to 1640°C, and the final carbon content is less than or equal to 0.07%, then the remaining molten steel and the attached refining slag in the aluminum-killed steel ladle are obtained and poured into the ladle to obtain the refining hot slag. The final slag in the converter is poured out according to the preset slag amount; The hot refined slag is poured into the converter. After the converter returns to the 0 position, the slag inside the converter is purged with a nitrogen purging gun. After the first preset time, the bottom blowing mode of the converter is adjusted to the strong stirring mode, and after the second preset time, the steel tapping process is carried out.

2. The dephosphorization treatment method for a converter according to claim 1, characterized in that, The method further includes: If the phosphorus content of the molten steel at the converter endpoint exceeds the standard by less than or equal to 0.005%, the endpoint temperature is greater than or equal to 1620°C, and the endpoint carbon content is less than or equal to 0.05%, then the remaining molten steel and the attached refining slag in the aluminum-killed steel ladle are obtained and poured into the ladle to obtain the refining hot slag.

3. A dephosphorization treatment method for a converter according to claim 1 or 2, characterized in that, The basicity of the refined hot slag is greater than or equal to 4, and the Al2O3 content of the refined hot slag is greater than or equal to 20%.

4. The dephosphorization treatment method for a converter according to claim 1, characterized in that, The preset slag dumping amount is within the range of one-half to three-quarters of the total slag amount at the end of the converter.

5. The dephosphorization treatment method for a converter according to claim 1, characterized in that, The position of the nitrogen purging gun is within the range of 1500mm to 1600mm.

6. The dephosphorization treatment method for a converter according to claim 1, characterized in that, The nitrogen pressure of the nitrogen purging gun is in the range of 0.85 MPa to 0.95 MPa.

7. The dephosphorization treatment method for a converter according to claim 1, characterized in that, The first preset time is within the range of 30s to 50s.

8. The dephosphorization treatment method for a converter according to claim 1, characterized in that, The bottom blowing intensity of the strong stirring mode is 5.54 Nm. 3 / (t·h).

9. The dephosphorization treatment method for a converter according to claim 1, characterized in that, The second preset time is within the range of 1 minute to 2 minutes.

10. A dephosphorization treatment method for a converter according to claim 1, characterized in that, The steps of adjusting the bottom blowing mode of the converter to the strong stirring mode after a first preset time, and then allowing it to stand for a second preset time before proceeding with the steel tapping process include: After the first preset time, the bottom blowing mode of the converter is adjusted to the strong stirring mode. After the second preset time, a sample is taken from the converter to determine the phosphorus content. If the phosphorus content is within the acceptable range, the steel tapping process will proceed.

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