Method for accurately controlling MgO in converter slag

Abstract

According to the method for accurately controlling the MgO in the converter slag, the slag fluidity is optimized by accurately controlling the adding amount of magnesium balls and dolomite in the smelting process and adding a modifier or the magnesium balls in the slag splashing process, so that the slag splashing furnace protection requirement is met, the dephosphorization capacity is improved, meanwhile, the steel material consumption is reduced, and the smelting stability and economical efficiency are improved. Starting from actual requirements of steel types, most steel types require low-phosphorus control, and slag with high MgO causes poor fluidity of the slag in the smelting process and poor dephosphorization effect. After the content of MgO in the slag is controlled, the charging mode is improved, and the slag charging time and batch are reasonably adjusted, so that the slag composition is stable, the dephosphorization capability is improved, the slag modification requirement is reduced, the consumption of steel and iron materials and flux is reduced, and the molten steel yield is improved. And the process controllability is optimized, so that the slag keeps stable chemical components and fluidity in the whole smelting process, abnormal fluctuation is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and particularly to a method for precisely controlling MgO in converter slag. Background Art

[0002] In order to increase the converter campaign life, it is usually necessary to ensure that the MgO content (w(MgO)) in the slag is above 10%. However, a high w(MgO) will affect the dephosphorization effect. Therefore, in the actual production process, measures such as increasing the basicity, lowering the carbon content at the end point, and secondary re-blowing are required to ensure the production of steel grades. These measures will result in a relatively high total iron content w(TFe) in the final slag, and thus additional post-tapping slag modification operations are needed, which not only increase the consumption of iron and steel materials and fluxes, but also increase the difficulty of converter lining protection operations and the control of the phosphorus content in steel grades. Therefore, how to optimize w(MgO) in the slag has become an urgent problem to be solved.

[0003] One of the characteristics of oxygen top-blown converter steelmaking is the fast smelting speed. In a short time, it is necessary to form a slag with appropriate basicity, good fluidity and containing a certain amount of FeO to ensure that the molten steel composition and temperature are qualified, while reducing the erosion of the furnace lining. The control of w(MgO) in the slag directly affects the fluidity and melting point of the slag, and thus affects the dephosphorization effect and the slag splashing lining protection effect. Therefore, studying a method for controlling w(MgO) based on adjusting the smelting feed materials not only can ensure the lining protection effect, but also can reduce the dephosphorization difficulty, which is of great significance. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to optimize and control w(MgO) in converter slag to meet the requirements of lining protection, and at the same time reduce the impact on dephosphorization, and provide a method for precisely controlling MgO in converter slag.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a method for precisely controlling MgO in converter slag, comprising the following steps:

[0006] (1) Reduce the saturation solubility of MgO in the slag, and reduce the saturation solubility of MgO by one or a combination of the following measures:

[0007] 1) Increase the slag basicity;

[0008] 2) Lower the smelting temperature;

[0009] 3) Adopt the bottom-blowing post-stirring process;

[0010] (2) Reduce the supersaturation of MgO in the slag, and reduce the supersaturation by one or a combination of the following measures:

[0011] ① Optimize the final slag basicity according to the requirements of the finished steel phosphorus content;

[0012] ②Based on the optimized static model, determine the addition amount of active lime and estimate the slag amount;

[0013] ③Based on the results of heat balance calculation, select the type and addition amount of magnesium-containing materials and complete the addition within the first 4 minutes of blowing;

[0014] (3) Optimize the slag-making system and control the addition time and batches of slag materials by adopting a batch feeding mode.

[0015] As a further improvement of the present invention: the formula for the saturated solubility of MgO in the converter slag in step (1):

[0016] ω(MgO) = 0.04(θ(℃) - 1650) + 0.28ω(TFe) - 2ω(CaO) / ω(SiO2) + 9.5

[0017] Calculate the saturated solubility of MgO.

[0018] As a further improvement of the present invention: increasing the basicity of the slag in step 1) includes adjusting the CaO / SiO2 ratio of the slag to make the basicity reach 3.0 - 3.6.

[0019] As a further improvement of the present invention: the tapping temperature in step 2) is controlled at 1618 - 1645 °C.

[0020] As a further improvement of the present invention: in the bottom blowing and post-stirring process in step 3), after the converter stops blowing, tilt the converter to the zero position, adjust the bottom blowing argon gas flow rate to 1 - 3 Nm 3 / h, and the stirring time is 60 - 120 seconds.

[0021] As a further improvement of the present invention: it can be seen from the formula for the saturated solubility of MgO in the slag that the saturated solubility of MgO is inversely proportional to the basicity and directly proportional to the temperature and the total iron content in the slag. Feasible measures to reduce the saturated solubility of MgO: ① Increase the basicity: Increasing the basicity can reduce the saturated solubility of MgO. However, in the actual steelmaking process, due to the influence of a high MgO content, in order to ensure the dephosphorization effect, the actual basicity has reached above 3.0, and increasing the basicity will increase the ash consumption; ② Reduce the temperature: Reducing the temperature can reduce the saturated solubility of MgO. However, in actual production control, considering the control of the cleanliness of molten steel, the temperature increase range during refining is restricted, so the space for reducing the tapping temperature is small; ③ Reduce the total iron content in the slag: 1) Extend the converter carbon-picking time, 2) Reduce the frequency of overoxidation and the reblowing time, 3) Develop a bottom blowing and post-stirring process. The post-stirring process is to tilt the converter to the zero position after the converter stops blowing and adjust the bottom blowing argon gas to an appropriate flow rate for stirring, which can significantly reduce the total iron content in the final slag.

[0022] As a further improvement of the present invention: In step ①, optimizing the basicity of the final slag includes controlling the basicity of the final slag at 2.99 - 3.6 according to the requirement of the finished product phosphorus content.

[0023] As a further improvement of the present invention: In step ③, the types of magnesium - containing materials for batching include light - burned magnesia powder, dead - burned magnesite or fused magnesite.

[0024] As a further improvement of the present invention: For slag splashing to protect the furnace in step (2), the requirement for the MgO content is to exceed the saturation solubility. If the MgO in the slag is to reach the saturated state, magnesium batching operation needs to be carried out during the smelting process. Determine the basicity of the final slag according to the requirement of the finished product phosphorus content of the smelted steel grade, and at the same time determine the addition amount of active lime based on the optimized static model to estimate the slag amount, then conduct a heat balance calculation according to the actual main raw materials charged into the furnace, and finally decide the types and addition amounts of magnesium - containing materials according to the slag amount and the results of the heat balance calculation.

[0025] As a further improvement of the present invention: In step (3), batch feeding includes at least two feedings. Among them, the first batch adds 80 - 90% of the active lime and part of the magnesium - containing materials, and the remaining part is added during the blowing process.

[0026] Application of the method for precisely controlling MgO in converter slag described above in the oxygen top - blown converter steelmaking production.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] After controlling the MgO content in the slag, the converter feeding mode is improved, making the converter slag meet the requirements of slag splashing to protect the furnace, while improving the dephosphorization ability. A more suitable slag can also reduce the consumption of iron and steel materials. By optimizing the control strategy of MgO, adjusting the basicity, temperature and total iron content in the slag, the fluidity and melting point of the slag are reasonably controlled, thereby improving the stability and economy of the steelmaking process. The optimized smelting process reduces the consumption of iron and steel materials and fluxes, reduces the production cost, increases the service life of the furnace lining, and reduces the additional slag modification operation after tapping, improving the production efficiency. Specific embodiments

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] During the converter steelmaking process, to extend the furnace life, it is usually necessary to maintain the MgO content in the slag above 10%. However, too high w(MgO) will reduce the dephosphorization effect. In production, the quality of steel grades is often ensured by increasing the basicity, reducing the end-point carbon content, secondary blowing, etc. These measures result in a relatively high total iron content in the final slag, and additional slag modification after tapping is required, which not only increases the consumption of iron and steel materials and fluxes, but also increases the difficulty of converter furnace lining protection and phosphorus component control. The control of w(MgO) in the slag directly affects its fluidity and melting point, and thus affects the dephosphorization efficiency and the effect of slag splashing for furnace lining protection.

[0032] At present, the common methods in actual production include maintaining production requirements by increasing the basicity, adjusting the end-point carbon content, secondary blowing, etc. However, these methods often lead to an increase in the total iron content (w(TFe)) in the final slag, which not only increases the difficulty of converter slag modification, but also additionally increases the consumption of iron and steel materials and fluxes. In addition, too high w(TFe) affects the furnace lining protection effect, shortens the furnace life, and increases the difficulty of controlling the phosphorus component in the steel grade. Therefore, studying a control method that can optimize the w(MgO) content in the slag, making it meet the furnace lining protection requirements and reduce the dephosphorization difficulty, is the key to improving the smelting stability and economy.

[0033] The present invention will be further described in conjunction with embodiments:

[0034] A method for precisely controlling MgO in converter slag, comprising the following steps:

[0035] (1) Reduce the saturation solubility of MgO in the slag, and reduce the saturation solubility of MgO by one or a combination of the following measures:

[0036] 1) Increase the basicity of the slag;

[0037] 2) Reduce the smelting temperature;

[0038] 3) Adopt the bottom blowing and post-stirring process;

[0039] (2) Reduce the supersaturation of MgO in the slag by one or a combination of the following measures to reduce the supersaturation:

[0040] ① Optimize the final slag basicity according to the required finished product phosphorus content of the steel grade;

[0041] ② Determine the addition amount of active lime and estimate the slag amount according to the optimized static model;

[0042] ③ Select the type and addition amount of magnesium-containing materials according to the results of heat balance calculation and complete the addition within the first 4 minutes of blowing;

[0043] (3) Optimize the slag-making system and control the addition time and batches of slag materials by using the batch feeding mode.

[0044] The present invention effectively reduces the saturated solubility of MgO in the slag by increasing the basicity, reducing the temperature and adopting the bottom blowing and post-stirring process, enhancing the stability of MgO in the slag, which is helpful for furnace protection, and at the same time avoiding excessive reduction of the dephosphorization efficiency. By reasonably controlling w(MgO) close to the saturated state, the slag not only has good furnace protection ability but also does not cause difficulty in dephosphorization due to too high MgO content. Optimize the final slag basicity according to the steel grade composition to ensure that the dephosphorization ability meets the production requirements and reduce the side effects caused by too high basicity. Use the static model and heat balance calculation to accurately determine the addition amounts of active lime and magnesium-containing materials, reduce unnecessary flux consumption, and improve the stability of the slag composition. Complete the addition of magnesium-containing materials within the first 4 minutes of blowing to ensure uniform distribution of MgO, improve the balance of slag-iron reaction, make the properties of the final slag more stable, and contribute to dephosphorization and furnace protection. Adopt the batch feeding mode to increase the slag formation speed, control the fluidity and melting point of the slag more accurately, and avoid the slag being too viscous or too dilute affecting furnace protection and dephosphorization. By reasonably controlling the addition time and batches of slag materials, reduce the waste of steel materials, fluxes and energy consumption, and improve the economy of the smelting process. Improve the durability of the furnace lining, reduce the need for slag modification, thereby reducing production costs and improving the stability and efficiency of converter operation.

[0045] As an embodiment of the present invention, the formula for the saturated solubility of MgO in the converter slag in step (1):

[0046] ω(MgO) = 0.04(θ(°C) - 1650) + 0.28ω(TFe) - 2ω(CaO) / ω(SiO2) + 9.5

[0047] Calculate the saturated solubility of MgO. Increasing the slag basicity includes adjusting the CaO / SiO2 ratio of the slag to make the basicity reach 3.0 - 3.6. In step 2), the tapping temperature is controlled at 1618 - 1645 °C. In step 3), in the bottom blowing and post-stirring process, after the converter stops blowing, tilt the converter to the zero position, adjust the bottom blowing argon flow rate to 1 - 3 Nm 3 / h, and the stirring time is 60 - 120 seconds.

[0048] It can be seen from the saturation solubility formula of MgO in slag that the saturation solubility of MgO is inversely proportional to the basicity, and directly proportional to the temperature and the total iron content in the slag. Feasible measures to reduce the saturation solubility of MgO: ① Increase the basicity: Increasing the basicity can reduce the saturation solubility of MgO. However, in the actual steelmaking process, due to the influence of a high MgO content, in order to ensure the dephosphorization effect, the actual basicity has reached above 3.0, and increasing the basicity will increase the ash consumption; ② Lower the temperature: Lowering the temperature can reduce the saturation solubility of MgO. However, in actual production control, considering the control of molten steel cleanliness, the temperature increase range during refining is limited, so the space for reducing the tapping temperature is small; ③ Reduce the total iron content in the slag: 1) Prolong the tapping carbon time in the converter, 2) Reduce the frequency of overoxidation and the reblowing time, 3) Develop a post-blowing process at the bottom. The post-blowing process is to swing the converter to the zero position after the converter stops blowing, and adjust the bottom blowing argon gas to an appropriate flow rate for stirring, which can significantly reduce the total iron content in the final slag.

[0049] By adjusting the CaO / SiO2 ratio of the slag, controlling the basicity within 3.0 - 3.6, reducing the saturation solubility of MgO, reducing the precipitation of excessive MgO, and improving the stability and furnace protection ability of the slag. Appropriately increasing the basicity can improve the fluidity of the slag, reduce the erosion of the furnace lining, and optimize the slag composition while ensuring the dephosphorization effect. By controlling the tapping temperature, reducing the influence of temperature on the solubility of MgO, reducing the precipitation amount of MgO, thus enhancing the furnace protection effect, and at the same time avoiding too low temperature affecting the quality of molten steel. Reducing the temperature within a reasonable range helps to reduce the supersaturated state of MgO, improve the stability of the slag, and make it more suitable for slag splashing furnace protection. Adopt the post-blowing process at the bottom. After the converter stops blowing, swing it to the zero position, and adjust the bottom blowing argon gas flow rate to 1 - 3 Nm 3 / h, and control the stirring time within 60 - 120 seconds, which can significantly reduce the total iron content in the final slag. By prolonging the tapping carbon time, reducing the frequency of overoxidation and the reblowing time, further reducing the FeO content in the slag, reducing the instability of the oxidation reaction, and improving the quality of the final slag. After the total iron content in the final slag is reduced, the viscosity and melting point of the slag are optimized, the dephosphorization ability is improved, the consumption of steel and iron materials is reduced at the same time, and the overall steelmaking process is made more efficient. By optimizing the control of basicity, temperature and total iron content, reducing the need for slag modification, reducing the consumption of fluxes, reducing the loss of steel and iron materials, and increasing the service life of the converter. By reasonably controlling the dissolution state of MgO, optimizing the furnace protection effect, reducing the erosion of the furnace lining, reducing the maintenance cost, and improving the stable operation ability of the converter.

[0050] As an embodiment of the present invention, in step (2), the requirement for the MgO content in slag splashing for furnace protection is that it only needs to exceed the saturation solubility. If the MgO in the slag is to reach the saturation state, the magnesium addition operation needs to be carried out during the smelting process to complete. Determine the final slag basicity according to the requirement of the finished product phosphorus content of the smelted steel grade, and at the same time determine the addition amount of active lime according to the optimized static model to estimate the slag amount, then conduct a heat balance calculation based on the actual main raw materials charged into the furnace, and finally determine the type and addition amount of the magnesium addition material according to the slag amount and the heat balance calculation results. Among them, optimizing the final slag basicity in step ① includes controlling the final slag basicity within 2.99 - 3.6 according to the requirement of the finished product phosphorus content. The types of magnesium addition materials in step ③ include light burned magnesia powder, dead burned magnesite or fused magnesia.

[0051] Since the requirement for the MgO content in slag splashing for furnace protection is that it only needs to exceed the saturation solubility, by performing the magnesium addition operation to make the MgO content reach the saturation state, it not only avoids the excessive viscosity of the slag caused by excessive MgO, which affects the fluidity, but also ensures that the slag has good furnace protection ability. Through heat balance calculation and reasonable selection of magnesium addition materials, while the slag meets the furnace protection requirements, it maintains an appropriate melting point and fluidity, avoids excessive erosion of the furnace lining, and improves the converter furnace life. According to the requirement of the finished product phosphorus content, control the final slag basicity within 2.99 - 3.6 to ensure that while taking into account furnace protection, it does not affect the dephosphorization ability of the slag and keeps the phosphorus content in the molten steel stable within the target range. Optimize the chemical composition of the slag by balancing the basicity to avoid the increase in flux consumption caused by too high basicity, and at the same time reduce the situation of affecting dephosphorization due to too low basicity. According to the optimized static model, determine the addition amount of active lime and estimate the slag amount to make the slag composition more balanced and avoid local MgO supersaturation or deficiency. Use different types of magnesium addition materials such as light burned magnesia powder, dead burned magnesite or fused magnesia, and select the optimal scheme according to different smelting conditions to ensure uniform distribution of MgO and improve the slag quality. Through scientific calculation of the slag amount and heat balance, reasonably determine the addition amount of the magnesium addition material, reduce unnecessary flux consumption, improve the smelting efficiency, and reduce the production cost. By optimizing the MgO content control strategy, reduce the need for slag modification, reduce the consumption of iron and steel materials, fluxes and energy, and improve the economic and environmental benefits of converter smelting. Make the slag reach the best balance between furnace protection and dephosphorization, improve the stability of the smelting process, reduce quality problems caused by slag composition fluctuations, and improve the purity of molten steel and product consistency. By optimizing the final slag basicity, accurately calculating the addition amount of the magnesium addition material and selecting the appropriate type of magnesium addition material, precise control of the MgO content in the slag is achieved. This scheme ensures that the slag can not only meet the requirements of slag splashing for furnace protection, but also improve the dephosphorization efficiency, while reducing the consumption of iron and steel materials and fluxes, improving the production stability and economic benefits, and providing a reliable guarantee for the efficient and stable converter steelmaking process.

[0052] As an embodiment of the present invention, the batch addition amount and time of the slag charge in step (3) have a direct impact on the slag formation speed. In order to ensure the dephosphorization ability during the smelting process while reducing the erosion of the furnace lining by the slag, the converter feeding mode adopts a batch feeding mode. The batch feeding includes at least two feedings. In the first batch, 80 - 90% of the activated lime and part of the magnesium-containing materials are added, and the remaining part is added during the blowing process.

[0053] Through the batch feeding mode, 80 - 90% of the activated lime and part of the magnesium-containing materials are added in the first batch, enabling the rapid formation of slag in the early stage, increasing the basicity, promoting the dephosphorization reaction, and improving the dephosphorization efficiency of the molten steel. Appropriately delaying the addition of the remaining slag charge gradually optimizes the basicity and fluidity of the slag, avoiding the slag becoming too thick and the fluidity decreasing due to the one-time addition of too much slag charge, which in turn affects the full progress of the dephosphorization reaction. Since the fluidity and melting point of the slag have an important impact on the erosion degree of the furnace lining, the batch feeding mode can avoid the uneven composition of the slag caused by one-time feeding, ensure good fluidity of the slag, thereby reducing the direct scouring and chemical erosion of the high-temperature slag on the furnace lining and increasing the service life of the furnace lining. Control the distribution of MgO and CaO in the slag to keep the chemical composition of the slag stable throughout the blowing process, avoiding uneven lining losses caused by too high or too low local basicity. By reasonably arranging the feeding time, reduce the excessive use of fluxes caused by uneven feeding, improve the utilization rate of the slag, and reduce production costs. Enable more efficient utilization of iron and steel materials and fluxes during the smelting process, reduce waste, and increase the yield of molten steel. The batch feeding mode makes the change of slag composition more stable, reduces the instability of the smelting process caused by the drastic fluctuation of slag composition, improves the process controllability, and reduces the incidence of abnormal situations. By optimizing the feeding sequence and time, improve the predictability of the converter smelting process, enhance the overall smelting efficiency, and improve the consistency of molten steel quality.

[0054] The following are specific embodiments of the present invention:

[0055] Example 1:

[0056] According to the heat balance calculation, 500 kg of dolomite and 400 kg of magnesium balls are added. A first-tap slag sample is obtained with R: 3.6, w(MgO): 6.8%, first-tap phosphorus: 0.025%, first-tap carbon: 0.097% (low TFe), and the first-tap slag is appropriate. The iron and steel material consumption for this furnace is 1055 kg / t.

[0057] The iron water sample of this furnace is waste. Without heat balance calculation, 800 kg of dolomite and 400 kg of magnesium balls are added. A first-tap slag sample is obtained with R: 3.19, w(MgO): 7.9%. Compared with furnace number 24103398, the basicity is lower, and the higher MgO content results in a higher first-tap phosphorus of 0.037%, a first-tap carbon of 0.06% (high TFe), and the first-tap slag is too viscous. The iron and steel material consumption for this furnace reaches 1069 kg / t.

[0058] Example 2:

[0059] According to the heat balance calculation, 500 kg of dolomite and 400 kg of magnesium balls were added. The dolomite was not completely added until 4 minutes later. The tapping temperature for the first time was 1625 °C (appropriate temperature), the carbon content at the first tapping was 0.07% (appropriate TFe), and the phosphorus content at the first tapping was 0.041% (high phosphorus). The R value of the slag sample obtained at the first tapping was 3.6 (appropriate), and w(MgO) was 2.67% (low). The slag was too thin to play a role in protecting the furnace, and the steel and iron materials consumption for this furnace was 1073 kg / t (relatively high).

[0060] According to the heat balance calculation, 800 kg of dolomite and 60 kg of magnesium balls were added. The magnesium-containing materials were added 4 minutes ago. The tapping temperature for the first time was 1636 °C, the carbon content at the first tapping was 0.10%, and the phosphorus content at the first tapping was 0.028%. The R value of the slag sample obtained at the first tapping was 3.27, and w(MgO) was 7.32%. The viscosity of the slag was appropriate, and the effect of slag splashing for furnace protection was good. The steel and iron materials consumption for this furnace was 1055 kg / t.

[0061] Example 3:

[0062] According to the heat balance calculation, 500 kg of dolomite and 100 kg of magnesium balls were added. The magnesium-containing materials were added 4 minutes ago. The tapping temperature for the first time was 1645 °C, the carbon content at the first tapping was 0.096%, and the phosphorus content at the first tapping was 0.038%. The R value of the slag sample obtained at the first tapping was 3.59, and w(MgO) was 9.12%. It can be seen from the slag sample that the high temperature led to an increase in the saturated solubility of MgO, and the slag was too viscous. The steel and iron materials consumption for this furnace was 1067 kg / t.

[0063] According to the heat balance calculation, 500 kg of dolomite and 300 kg of magnesium balls were added. The magnesium-containing materials were added 4 minutes ago. The tapping temperature for the first time was 1618 °C, the carbon content at the first tapping was 0.079%, and the phosphorus content at the first tapping was 0.018%. The R value of the slag sample obtained at the first tapping was 2.99, and w(MgO) was 6.65%. The slag was appropriate and the furnace protection effect was good. The steel and iron materials consumption for this furnace was 1053 kg / t.

[0064] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these examples do not limit the scope of the present application. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0065] In summary, after those of ordinary skill in the art read the documents of the present invention, various other corresponding transformation schemes made without creative mental labor according to the technical solutions and technical concepts of the present invention all fall within the scope protected by the present invention.

Claims

1. A method for precisely controlling MgO in converter slag, characterized in that It includes the following steps: (1) Reduce the saturated solubility of MgO in the slag, and reduce the saturated solubility of MgO by one or a combination of the following measures: 1) Increase the slag basicity; 2) Lower the smelting temperature; 3) Adopt the bottom-blowing and post-stirring process; (2) Reduce the supersaturation of MgO in the slag, and reduce the supersaturation by one or a combination of the following measures: ① Optimize the final slag basicity according to the required finished steel phosphorus content; ② Determine the addition amount of active lime and estimate the slag amount according to the optimized static model; ③ Select the type and addition amount of magnesium-containing materials according to the results of heat balance calculation, and complete the addition within the first 4 minutes of blowing; (3) Optimize the slag-making system, and control the addition time and batches of slag materials by adopting a batch feeding mode.

2. The method for precisely controlling MgO in converter slag according to claim 1, wherein The formula for the saturated solubility of MgO in the converter slag in step (1): ω(MgO)=0.04(θ(℃)-1650)+0.28ω(TFe)-2ω(CaO) / ω(SiO2)+9.5 is used to calculate the saturated solubility of MgO.

3. A method for precisely controlling MgO in converter slag according to claim 2, characterized in that, In step 1), increasing the slag basicity includes adjusting the CaO / SiO2 ratio of the slag to make the basicity reach 3.0-3.

6.

4. A method for precisely controlling MgO in converter slag according to claim 1, characterized in that, In step 2), the tapping temperature is controlled at 1618-1645°C.

5. A method for precisely controlling MgO in converter slag according to claim 1, characterized in that In step 3), after the converter stops blowing, the converter is tilted to the zero position and the flow rate of bottom-blown argon is adjusted to 1-3 Nm 3 / h, and the stirring time is 60-120 seconds.

6. A method for precisely controlling MgO in converter slag according to claim 1, characterized in that In step ①, optimizing the final slag basicity includes controlling the final slag basicity at 2.99-3.6 according to the required finished steel phosphorus content.

7. A method for precisely controlling MgO in converter slag according to claim 6, characterized in that, The types of magnesium-containing materials in step ③ include light-burned magnesium powder, dead-burned magnesite or fused magnesite.

8. A method for precisely controlling MgO in converter slag according to claim 7, characterized in that, In step (3), batch feeding includes at least two feedings. Among them, 80-90% of the active lime and part of the magnesium-containing materials are added in the first batch, and the remaining part is added during the blowing process.

9. Application of a method for precisely controlling MgO in converter slag according to any one of claims 1-8 in oxygen top-blown converter steelmaking production.