Method of steelmaking with dephosphorization in converter

Abstract

The application provides a dephosphorization smelting method in a converter, comprising the following steps: performing oxygen blowing smelting on molten steel in the converter, reaching an oxygen blowing smelting endpoint, obtaining first molten steel, the carbon content in the first molten steel being 0.02%-0.05%, and the temperature of the first molten steel being 1580-1630 DEG C; switching the oxygen blowing to nitrogen blowing, performing nitrogen blowing smelting on the first molten steel, reaching a nitrogen blowing smelting endpoint after the molten steel in the converter reaches a preset temperature, obtaining converter molten steel, and the preset temperature being 1550-1570 DEG C. The smelting method can stably control the phosphorus content of the molten steel to be ≤0.01% by controlling the oxygen blowing endpoint parameter and the nitrogen blowing process, and meets the production requirements of ultralow phosphorus steel; meanwhile, oxygen blowing is not needed, the loss of iron and steel materials is reduced, the production cost is significantly reduced, the problems of supplementary blowing and excessively dilute slag are reduced, the erosion rate of the furnace lining is reduced, the service life of the furnace lining is prolonged, and the converter operation rate and production efficiency are improved.

Description

Technical Field

[0001] This application belongs to the field of iron and steel smelting technology, and in particular relates to a smelting method for dephosphorization in a converter. Background Technology

[0002] In converter smelting, phosphorus content is one of the key indicators affecting steel quality, especially for high-end steel products where strict control of phosphorus content is required. In traditional processes, if the phosphorus content is below standard after oxygen blowing, further dephosphorization is necessary through supplementary oxygen blowing. However, supplementary blowing increases steel material loss, accelerates furnace lining erosion, and may cause slag entrapment due to excessively thin slag, leading to fluctuations in phosphorus content. Therefore, how to achieve efficient dephosphorization without supplementary blowing after oxygen blowing is a pressing technical problem to be solved in this field. Summary of the Invention

[0003] In view of this, this application provides a smelting method for dephosphorization in a converter, which can improve dephosphorization efficiency, stabilize the phosphorus content of molten steel, reduce production costs, and improve product quality.

[0004] This application provides a smelting method for dephosphorization in a converter, comprising the following steps: oxygen blowing smelting of molten steel in a converter, reaching the oxygen blowing smelting endpoint to obtain first molten steel, wherein the carbon content of the first molten steel is 0.02%-0.05%, and the temperature of the first molten steel is 1580℃-1630℃; switching oxygen blowing to nitrogen blowing, nitrogen blowing smelting of the first molten steel, and reaching the nitrogen blowing smelting endpoint after the molten steel in the converter reaches a preset temperature, to obtain converter molten steel, wherein the preset temperature is 1550-1570℃.

[0005] According to an embodiment of this application, the nitrogen blowing gun position is maintained at 1.5-2.5 meters.

[0006] According to an embodiment of this application, during nitrogen blowing, the position of the oxygen lance is dynamically adjusted with the blowing time: the position is maintained at 2.0-2.5 meters for the first 0-2 minutes of nitrogen blowing, and then adjusted to 1.5-2.0 meters.

[0007] According to the embodiments of this application, the nitrogen blowing intensity is 3.57-4.76 m. 3 / min.t.

[0008] According to an embodiment of this application, during the nitrogen blowing process, the stirring power density of the molten steel is controlled at 1.89-2.36 kW / ton of steel to enhance the reaction between the molten steel and the slag.

[0009] According to an embodiment of this application, the nitrogen blowing time is determined based on the temperature difference between the first molten steel and a preset temperature: when the temperature difference is 30-80°C, the nitrogen blowing time is 2-8 minutes.

[0010] According to the embodiments of this application, the molten steel is allowed to stand for 0.5-2 minutes after nitrogen blowing is completed.

[0011] According to embodiments of this application, slag formation is controlled during the converter smelting process so that the final slag has dephosphorization capability.

[0012] According to an embodiment of this application, the phosphorus content of the converter steel is ≤0.01%.

[0013] The dephosphorization smelting method in the converter of this application can stably control the phosphorus content of molten steel to ≤0.01% by controlling the oxygen blowing endpoint parameters and nitrogen blowing process, which meets the requirements for ultra-low phosphorus steel production. At the same time, there is no need to add oxygen, which reduces steel material loss and significantly reduces production costs. It also reduces the problems of adding oxygen and excessively thin slag, reduces the furnace lining erosion rate, extends the furnace lining life, and improves the converter operating rate and production efficiency. Detailed Implementation

[0014] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0015] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0016] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0017] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0018] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0019] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0020] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0021] Unless otherwise specified, this application uses conventional testing methods or testing methods recommended by the instrument.

[0022] Traditional methods require supplemental oxygen blowing for dephosphorization, but this leads to increased steel material loss, higher production costs, and may also worsen furnace conditions, such as accelerating furnace lining erosion. Furthermore, excessively thin slag can easily cause slag entrapment, resulting in excessive phosphorus content and making it difficult to meet the production requirements of ultra-low phosphorus steel.

[0023] In view of the above problems, this application provides a smelting method for dephosphorization in a converter, which can improve dephosphorization efficiency, stabilize the phosphorus content of molten steel, reduce production costs, and improve product quality.

[0024] The smelting method for dephosphorization in a converter provided in this application includes the following steps:

[0025] S100: Oxygen blowing is used to smelt molten steel in a converter until the oxygen blowing smelting endpoint is reached, resulting in the first molten steel. The carbon content of the first molten steel is 0.02%-0.05%, and the temperature of the first molten steel is 1580℃-1630℃.

[0026] S200: Switch from oxygen blowing to nitrogen blowing to smelt the first molten steel with nitrogen. Once the molten steel in the converter reaches the preset temperature, the nitrogen blowing smelting endpoint is reached, and converter molten steel is obtained. The preset temperature is 1550-1570℃.

[0027] The dephosphorization smelting method in the converter provided in this application embodiment can achieve efficient dephosphorization without the need for supplementary blowing. By controlling the oxygen blowing endpoint parameters and the nitrogen blowing process, the phosphorus content of molten steel can be stably controlled.

[0028] In this embodiment, the carbon content at the oxygen blowing endpoint is limited to a low carbon range of 0.02%-0.05%. This carbon content range ensures that the TFe (iron oxide) content in the slag is maintained at a suitable dephosphorization level, while also ensuring that the slag is fully melted and has good fluidity. This creates favorable conditions for the full dephosphorization reaction between the molten steel and the slag during the subsequent nitrogen blowing process, avoiding adverse effects caused by excessively high carbon content leading to slag stickiness and reaction inhibition, or excessively low carbon content leading to excessively strong oxidizing properties in the slag.

[0029] When nitrogen is blown in, the carbon content in the molten steel is high, and the dissolved oxygen activity is low, which inhibits the reaction between oxidizing gases and N2. The blown N2 bubbles dissolve in the molten steel through mass transfer at the gas-liquid interface, conforming to Sieverts' law w[N]=k·√p(N2), where k is the dissolution constant and p(N2) is the nitrogen partial pressure. At this time, the content of reducing elements such as [C] in the molten steel is high, which can reduce any small amount of oxides that may exist on the surface of the molten steel, eliminating the obstacle of the interfacial oxide film to the dissolution of N2; at the same time, the low-oxygen environment reduces the reaction of N2 and O2 to produce NO. x The consumption of N2 is such that the dissolution rate of N2 is greater than the escape rate, resulting in increased nitrogen content in the molten steel.

[0030] In this embodiment, the carbon content at the end of oxygen blowing is within the lower range mentioned above. At the end of oxygen blowing, the carbon content is low, and the dissolved oxygen activity in the molten steel is high. The blown-in N2 preferentially reacts with the dissolved oxygen, generating NO, which is gaseous and has extremely low solubility. This NO escapes with the furnace gas, resulting in N2 consumption. Furthermore, in a high-oxygen environment, FeO and other oxide films easily form on the surface of the molten steel, increasing the interfacial mass transfer resistance between N2 bubbles and the molten steel, and reducing the N2 dissolution rate. Simultaneously, the dissolution constant k in Sievts' law decreases with increasing dissolved oxygen, further inhibiting N2 dissolution. Ultimately, the amount of N2 dissolved is far lower than the amount consumed and escaped, thus avoiding the risk of increased nitrogen levels.

[0031] For example, the carbon content at the end of oxygen blowing is 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, or a range of any two of the above values.

[0032] In this embodiment, the oxygen blowing endpoint temperature is precisely controlled between 1580℃ and 1630℃. This temperature range can reasonably control the endpoint phosphorus content, ensure good fluidity of molten steel, balance dephosphorization efficiency and molten steel fluidity, and stabilize the smelting rhythm.

[0033] If the temperature is too high, the final phosphorus content will increase, the nitrogen blowing and cooling time will be prolonged, and the phosphorus content after nitrogen blowing will fluctuate drastically and the smelting process will be prolonged. If the temperature is too low, the scrap steel will not melt completely, the temperature drop after nitrogen blowing will be too large, and it may lead to supplementary blowing operations, which is not conducive to the effective control of the final phosphorus content, and it is also easy to cause slag entrapment during the tapping process.

[0034] Therefore, precisely controlling the oxygen blowing endpoint temperature within the range of 1580℃-1630℃ provides a foundation for the stable operation of the subsequent nitrogen blowing process and ensures that the smelting rhythm is controllable.

[0035] For example, the final oxygen blowing temperature is 1580℃, 1585℃, 1590℃, 1595℃, 1600℃, 1605℃, 1610℃, 1615℃, 1620℃, 1625℃, 1630℃ or a range of any two of the above values.

[0036] After oxygen blowing ends, nitrogen blowing is switched off instead of replenishing oxygen. Nitrogen blowing enhances the mixing effect of molten steel, promotes the mixing of molten steel and slag, and effectively reduces the temperature of molten steel, thus promoting the continuous dephosphorization reaction. As an inert gas, nitrogen avoids the oxidation loss of steel materials and furnace lining erosion caused by replenishing oxygen, while also reducing the risk of excessively thin slag, thus solving the problems caused by replenishing oxygen blowing at its root.

[0037] In this embodiment of the application, by controlling the oxygen blowing endpoint parameters and the nitrogen blowing process, the phosphorus content of molten steel can be stably controlled at ≤0.01%, meeting the requirements for ultra-low phosphorus steel production; at the same time, there is no need to add oxygen, reducing steel material loss and significantly reducing production costs; reducing the problems of supplementary blowing and excessively thin slag, reducing the furnace lining erosion rate, extending the furnace lining life, and improving converter operation rate and production efficiency.

[0038] In some embodiments, the preset temperature is 1550-1570°C.

[0039] One of the core functions of nitrogen blowing is to lower the temperature of molten steel through stirring, creating a more favorable low-temperature environment for the dephosphorization reaction. This is because dephosphorization is an exothermic reaction, and low temperatures promote its forward propagation. The initial molten steel temperature at the end of oxygen blowing is 1580-1630℃, and the nitrogen blowing process needs to lower the temperature to 1550-1570℃, with the temperature difference controlled within 10-80℃. This ensures sufficient temperature reduction to promote dephosphorization while avoiding adverse effects caused by excessive cooling.

[0040] If the temperature is too low after nitrogen blowing, the fluidity of the molten steel will decrease, the slag-steel separation ability will weaken, and slag inclusions will easily occur, causing slag to mix into the molten steel and reducing the purity of the molten steel. At the same time, during the argon blowing process in the ladle, the stirring effect of the low-temperature molten steel will be poor, making it difficult to remove gases and inclusions from the molten steel, which will affect the stability of subsequent refining processes.

[0041] If the temperature after nitrogen blowing exceeds 1570℃, the driving force for the dephosphorization reaction will be insufficient, and the phosphorus in the molten steel will be difficult to be fully transferred to the slag, resulting in insufficient dephosphorization and failing to meet the quality requirements of ultra-low phosphorus steel with a phosphorus content of ≤0.01%. At high temperatures, the oxidizing properties of the slag will be enhanced, which may aggravate the secondary oxidation of the molten steel and affect the stability of the steel composition.

[0042] By strictly controlling the temperature after nitrogen blowing at 1550-1570℃, this invention effectively avoids the problems of steel slag separation caused by low temperature and insufficient dephosphorization caused by high temperature while ensuring dephosphorization efficiency, providing a key guarantee for high-quality output of converter steel.

[0043] For example, the preset temperature after nitrogen blowing is 1550℃, 1552℃, 1554℃, 1555℃, 1556℃, 1558℃, 1560℃, 1562℃, 1564℃, 1565℃, 1566℃, 1568℃, 1570℃ or any range of two of the above values.

[0044] In actual production, the preset temperature can be precisely controlled through the following methods:

[0045] The nitrogen blowing time is dynamically adjusted according to the temperature difference between the oxygen blowing endpoint temperature and the preset temperature: for every 10℃ increase in temperature difference, the nitrogen blowing time is extended by 1-1.5 minutes. For example, when the endpoint temperature is 1630℃, nitrogen blowing is required for 5-8 minutes to reduce the temperature to 1550-1570℃.

[0046] By combining the stepwise adjustment of the nitrogen blowing flow rate, the flow rate is slightly higher in the early stage to quickly cool down the temperature, and slightly lower in the later stage to stabilize the temperature and avoid temperature fluctuations exceeding the range.

[0047] In some embodiments, the nitrogen blowing gun is positioned at 1.5-2.5 meters.

[0048] The lance position refers to the vertical distance between the oxygen lance nozzle and the surface of molten steel in the converter during the converter smelting process. The same oxygen lance is used during nitrogen blowing operations.

[0049] During nitrogen blowing, the position of the oxygen lance directly affects the interaction between nitrogen and molten steel. After nitrogen is injected into the furnace through the oxygen lance, the lance height determines the depth of nitrogen impact on the molten steel, the stirring range, and the intensity of disturbance to the slag. Controlling the lance position between 1.5 and 2.5 meters can enhance the stirring of the molten steel to promote the dephosphorization reaction, while avoiding adverse effects caused by the lance position being too high or too low.

[0050] If the lance position is below 1.5 meters, the nitrogen impact depth increases, resulting in excessive stirring. This intensifies the scouring of the furnace bottom and molten pool by the molten steel, accelerating the erosion of the refractory materials in these areas, shortening the furnace service life, and affecting production flow and costs. If the lance position is above 2.5 meters, meaning the oxygen lance is far from the molten steel surface, the impact force weakens, and the stirring intensity of the molten steel is insufficient. This prevents the formation of sufficient circulation to fully mix the molten steel and slag, worsening the kinetics of the dephosphorization reaction. Phosphorus is difficult to transfer from the molten steel to the slag. Insufficient stirring also leads to uneven steel temperature distribution, affecting the uniformity of nitrogen cooling and potentially causing localized excessively high or low temperatures, which is detrimental to the stable control of the dephosphorization effect.

[0051] By controlling the gun position at 1.5-2.5 meters, this invention achieves a balance between stirring intensity and safety during nitrogen blowing, providing suitable kinetic conditions for the dephosphorization reaction.

[0052] For example, during nitrogen blowing operations, the nozzle position is 1.5 meters, 1.6 meters, 1.7 meters, 1.8 meters, 1.9 meters, 2.0 meters, 2.1 meters, 2.2 meters, 2.3 meters, 2.4 meters, 2.5 meters, or any combination of two of the above values.

[0053] In actual production, the lance position can be fine-tuned according to different stages of nitrogen blowing. For example, in the early stage of nitrogen blowing, the lance position can be controlled at 2.0-2.5 meters to allow the nitrogen gas to diffuse initially and avoid excessive initial impact. In the middle and later stages of nitrogen blowing, the position can be adjusted to 1.5-2.0 meters to enhance local stirring by lowering the lance position, promote the deep reaction between molten steel and slag, and ensure the dephosphorization effect.

[0054] In some embodiments, the oxygen lance position is dynamically adjusted during the nitrogen blowing process: the lance position is maintained at 2.0-2.5 meters for the first 0-2 minutes of nitrogen blowing, and then adjusted to 1.5-2.0 meters.

[0055] In the initial stage of nitrogen blowing, the molten steel is still at a relatively high temperature after oxygen blowing, and the mixing state of the slag and molten steel is not yet stable. At this time, controlling the lance position at a relatively high level of 2.0-2.5 meters serves several purposes: reducing the direct impact intensity of nitrogen on the surface of the molten steel, preventing molten steel splashing and causing the oxygen lance to stick to the steel, thus ensuring production safety; and allowing nitrogen to act on the surface of the molten steel with a wider diffusion range, initially promoting the uniform mixing of slag and molten steel, laying the foundation for the full-scale dephosphorization reaction in the future.

[0056] Two minutes after nitrogen blowing, the temperature of the molten steel has decreased somewhat due to initial stirring, and the slag and molten steel have formed a certain degree of mixing. At this point, the lance position is lowered to a relatively low level of 1.5-2.0 meters. The main purposes are: to enhance the impact depth of nitrogen on the molten steel and the intensity of local stirring, promoting a stronger circulation in the molten steel, allowing phosphorus in the molten steel to come into more sufficient contact with the slag with dephosphorizing capabilities, strengthening the kinetic conditions of the dephosphorizing reaction, and promoting the continuous and efficient dephosphorizing reaction; and to adapt to the state after the molten steel temperature decreases, compensating for the reduced fluidity of the molten steel that may be caused by the temperature drop by increasing the stirring intensity, ensuring that the slag and molten steel maintain a good reaction interface throughout the nitrogen blowing process, and avoiding incomplete dephosphorization due to insufficient stirring in the later stages.

[0057] This application embodiment, by dynamically adjusting the lance position according to the nitrogen blowing time, takes into account both the safety and basic construction of the mixing foundation in the early stage of nitrogen blowing, and ensures the stirring intensity required for the dephosphorization reaction in the middle and later stages. This allows the nitrogen blowing operation to adapt to the state of molten steel at different stages, thereby further improving the dephosphorization efficiency and stability after the converter oxygen blowing ends.

[0058] In some embodiments, the nitrogen blowing intensity is 3.57-4.76 m. 3 / min.t.

[0059] Nitrogen blowing flow rate is a crucial parameter determining the intensity of steel stirring and cooling efficiency; the nitrogen blowing intensity should be controlled between 3.57-4.76 m. 3 / min.t can enhance the mixing and contact between molten steel and slag through the impact and stirring of nitrogen, providing a sufficient reaction interface for the dephosphorization reaction. It can also effectively reduce the temperature of molten steel through the heat absorption and stirring of nitrogen, promoting the forward progress of the dephosphorization reaction. Thus, after the oxygen blowing ends, it can continuously promote the transfer of phosphorus from molten steel to slag.

[0060] If the nitrogen blowing intensity is less than 3.57m 3 A nitrogen blowing rate of / min.t results in insufficient impact force of nitrogen on molten steel, weakened stirring intensity, and difficulty in fully mixing molten steel and slag. This deteriorates the kinetic conditions of the dephosphorization reaction, preventing phosphorus from being efficiently transferred from molten steel to slag, leading to incomplete dephosphorization. The slowed cooling rate and prolonged nitrogen blowing time not only affect the smelting rhythm but may also cause accelerated furnace lining erosion due to the prolonged residence time of molten steel at higher temperatures. This can lead to phosphorus that has already entered the slag dissolving back into the molten steel, reducing the dephosphorization effect.

[0061] If the nitrogen blowing intensity is higher than 4.76m 3A temperature of / min.t can cause excessive nitrogen impact, intensifying the surging of molten steel and potentially leading to slag splashing and molten steel spraying. This results in increased steel loss and furnace lining erosion, while also disrupting the stable structure of the slag, such as causing fluctuations in slag oxidizability. An excessively rapid cooling rate can cause the molten steel temperature to drop below the preset range of 1550-1570℃ in a short period, leading to poor steel-slag separation, slag inclusions during tapping, and other problems that affect the quality of the molten steel.

[0062] The nitrogen blowing intensity also applies to the slag splashing operation standards during the nitrogen blowing stage in converters, and can be fine-tuned according to the converter capacity, the final oxygen blowing temperature, and the state of the molten steel. For example, for large-capacity converters of 200 tons or above, or when the final oxygen blowing temperature is high, approaching 1630℃, an intensity of 4.29-4.76m can be used. 3 A flow rate of / min.t is used to enhance stirring and cooling effects; for small to medium-capacity converters of 100-200 tons or when the oxygen blowing endpoint temperature is low, close to 1580℃, a flow rate of 3.57-4.29m can be used. 3 Nitrogen blowing intensity of / min.t should be maintained to avoid excessive stirring and cooling.

[0063] By controlling the nitrogen blowing intensity at 3.57-4.76m 3 / min.t, this invention ensures dephosphorization efficiency while taking into account production safety and process stability, providing reliable parameter support for efficient dephosphorization after oxygen blowing.

[0064] In some embodiments, during nitrogen blowing, the stirring power density of molten steel is controlled at 1.89-2.36 kW / ton of steel to enhance the reaction between molten steel and slag.

[0065] Controlling the molten steel to 1.89-2.36 kW / ton of steel ensures that the molten steel forms a suitable circulation and mixing state: on the one hand, sufficient stirring intensity breaks the interface layer between the molten steel and the slag, allowing the slag and molten steel to mix fully and promoting the transfer of phosphorus from the molten steel to the slag; on the other hand, it avoids the adverse effects of excessive or insufficient stirring on the dephosphorization effect, and provides a stable reaction environment for continuous dephosphorization after oxygen blowing ends.

[0066] Excessive stirring power density can lead to over-stirring of molten steel. Over-stirring can also make it difficult to separate molten steel from slag, increasing the risk of slag entrapment during tapping and causing phosphorus that has already entered the slag to re-mix into the molten steel, resulting in a rebound in phosphorus content. At the same time, excessive stirring power will intensify the erosion of the furnace lining, shorten the furnace lining life, and is not conducive to furnace stability.

[0067] In practice, the stirring power density range is achieved through the coordinated control of nitrogen flow rate and oxygen lance position.

[0068] When the nitrogen blowing flow rate is controlled according to the slag splashing standard and the gun position is maintained at 1.5-2.5 meters, a stirring power density of 1.89-2.36 kW / ton of steel can be formed. When the flow rate increases or the gun position decreases, the stirring power density increases; when the flow rate decreases or the gun position increases, the stirring power density decreases.

[0069] In some embodiments, the nitrogen blowing time is determined based on the temperature difference between the first molten steel and a preset temperature: when the temperature difference is 30-80°C, the nitrogen blowing time is 2-8 minutes.

[0070] When the temperature difference is 30-50℃: the required cooling range is smaller, and the nitrogen blowing time should be controlled within 2-5 minutes. A shorter nitrogen blowing time ensures the molten steel temperature drops to the preset range while avoiding excessive slag agitation due to prolonged stirring, reducing the risk of slag entrapment. Simultaneously, at this temperature difference, the initial temperature of the molten steel is relatively close to the preset value, allowing the dephosphorization reaction to proceed fully within a short time without the need for extended stirring.

[0071] When the temperature difference is 50-80℃: a larger temperature reduction is required, and the nitrogen blowing time needs to be extended to 5-8 minutes. A longer nitrogen blowing time can ensure that the molten steel temperature steadily drops to the target range. At the same time, continuous stirring ensures that the molten steel and slag are in full contact, ensuring that phosphorus has enough time to transfer from the molten steel to the slag, and avoiding poor dephosphorization effect due to insufficient cooling or insufficient reaction time.

[0072] In some embodiments, the molten steel is allowed to stand for 0.5-2 minutes after nitrogen blowing is completed.

[0073] During nitrogen blowing, nitrogen gas, through stirring, promotes thorough mixing of molten steel and slag, creating a favorable interface for the dephosphorization reaction. However, this also causes some low-density slag to be drawn into the molten steel due to the stirring kinetic energy, forming suspended fine slag particles. After nitrogen blowing, allowing the mixture to stand for 0.5-2 minutes allows sufficient time for the suspended slag particles to float, utilizing the density difference between the molten steel and slag, thus reducing the residual slag content in the molten steel. Simultaneously, the slower flow of molten steel during this settling period allows the fine slag particles to collide and aggregate, forming larger slag clumps. These clumps are more likely to float quickly to the converter slag layer during subsequent tapping, reducing slag inclusions from the source.

[0074] For example, the settling time is 0.5 minutes, 1 minute, 1.5 minutes or 2 minutes.

[0075] In some embodiments, slag formation is controlled during converter smelting to enable the final slag to have dephosphorization capabilities.

[0076] Slag formation refers to the process of fully melting and reacting the added slag-forming materials during the entire converter smelting process to form a slag with uniform composition and suitable fluidity. The key is to strictly control the TFe content in the slag within an appropriate range. TFe is an important indicator of slag oxidizability; excessively high or low TFe content will affect the dephosphorization capacity of the final slag. Insufficient TFe results in weak slag oxidizability, making it difficult to oxidize phosphorus in molten steel into phosphates that can be absorbed by the slag. Excessive TFe, on the other hand, may lead to overly thin slag, compromising its stability and hindering phosphorus fixation. Through full-process slag formation, the final slag must possess good oxidizability, basicity, and fluidity to provide a sufficient reaction carrier for the dephosphorization reaction.

[0077] To achieve complete slag formation, a suitable slag-forming agent must first be added. During the smelting process, fluorite, iron ore, and other slag-forming agents are added in a timely manner according to the slag's condition. The amount added is typically 5%-15% of the total lime content. These agents lower the slag's melting point, improve its fluidity, and promote the rapid melting of slag-forming materials such as lime, preventing the slag from becoming sticky and agglomerated. Then, during the oxygen blowing stage, the contact between oxygen, molten steel, and slag is controlled by adjusting the oxygen lance position. When the lance position is too high, the oxygen mainly reacts with the slag, enhancing its oxidizing properties; when the lance position is too low, the oxygen reacts more with the molten steel, indirectly promoting slag melting by increasing the steel temperature. Throughout the process, the lance position is fine-tuned in real-time based on slag fluidity monitoring results to ensure the slag is completely melted 3-5 minutes before the end of oxygen blowing.

[0078] After oxygen blowing, phosphorus in the molten steel needs to be adsorbed and fixed by reacting with the final slag. If the final slag is not fully slagified, the reaction interface between the slag and the molten steel is limited, and phosphorus cannot be absorbed efficiently. The fully slagified final slag can fully contact the molten steel with the help of stirring during the subsequent nitrogen blowing process, and continue to play the dephosphorization function. This avoids the interruption of the dephosphorization reaction due to poor slag condition, thereby achieving a stable reduction in phosphorus content without additional blowing.

[0079] In some embodiments, the phosphorus content of the converter steel is ≤0.01%.

[0080] Example

[0081] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0082] Example 1

[0083] The smelting method for dephosphorization in a converter according to this embodiment includes the following steps:

[0084] (1) Slag formation throughout the converter process.

[0085] (2) The molten steel in the converter is subjected to oxygen blowing smelting. The first molten steel is obtained when the oxygen blowing smelting endpoint is reached. The endpoint temperature is controlled at 1630℃, the endpoint carbon is controlled at 0.04%, and the endpoint phosphorus is 0.0143%.

[0086] (3) Nitrogen blowing is performed on the oxygen lance inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 3.81 m. 3 / min.t; The stirring power density of molten steel is controlled at 1.89kW / ton of steel, and the nitrogen blowing time is 7.5min.

[0087] (4) Control the temperature after nitrogen blowing at 1555℃.

[0088] (5) After the nitrogen blowing is completed, let the molten steel stand for 1.5 minutes.

[0089] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0068%, the fluidity of the steel was normal, and no slag entrapment occurred in the later stage of tapping.

[0090] Example 2

[0091] The smelting method for dephosphorization in a converter according to this embodiment includes the following steps:

[0092] (1) Slag formation throughout the converter process.

[0093] (2) The molten steel in the converter is subjected to oxygen blowing smelting. When the oxygen blowing smelting endpoint is reached, the first molten steel is obtained. The endpoint temperature is controlled at 1623℃, the endpoint carbon is controlled at 0.03%, and the endpoint phosphorus is 0.0133%.

[0094] (3) Nitrogen blowing is performed on the oxygen lance inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 3.81 m. 3 / min.t; The stirring power density of molten steel is controlled at 1.89kW / ton of steel, and the nitrogen blowing intensity and time are 6min.

[0095] (4) Control the temperature after nitrogen blowing at 1565℃.

[0096] (5) After the nitrogen blowing is completed, let the molten steel stand for 1 minute.

[0097] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0073%, with no slag entrapment and normal steel fluidity. In this example, allowing the molten steel to stand after nitrogen blowing reduced the likelihood of slag inclusions later.

[0098] Example 3

[0099] The smelting method for dephosphorization in a converter according to this embodiment includes the following steps:

[0100] (1) Slag formation throughout the converter process.

[0101] (2) The molten steel in the converter is subjected to oxygen blowing smelting. When the oxygen blowing smelting endpoint is reached, the first molten steel is obtained. The endpoint temperature is controlled at 1610℃, the endpoint carbon is controlled at 0.025%, and the endpoint phosphorus is 0.012%.

[0102] (3) Nitrogen blowing is performed using oxygen lances inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 4.29 m. 3 / min.t; The stirring power density of molten steel is controlled at 2.13kW / ton of steel, and the nitrogen blowing time is 6min.

[0103] (4) Control the temperature after nitrogen blowing at 1550℃.

[0104] (5) After the nitrogen blowing is completed, let the molten steel stand for 1.5 minutes.

[0105] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0060%, with no slag entrapment and normal steel fluidity. In this embodiment, the nitrogen blowing flow rate was increased and the settling time was longer, making slag entrapment less likely even at low temperatures.

[0106] Example 4

[0107] The smelting method for dephosphorization in a converter according to this embodiment includes the following steps:

[0108] (1) Slag formation throughout the converter process.

[0109] (2) The molten steel in the converter is subjected to oxygen blowing smelting. The first molten steel is obtained when the oxygen blowing smelting endpoint is reached. The endpoint temperature is controlled at 1605℃, the endpoint carbon is controlled at 0.026%, and the endpoint phosphorus is 0.0115%.

[0110] (3) Nitrogen blowing from the oxygen lance inside the converter; the lance position is maintained at 2.2 meters for the first 0-2 minutes of nitrogen blowing, and then adjusted to 1.6 meters for the next 2-7 minutes; the nitrogen blowing intensity is 3.81m. 3 / min.t; The stirring power density of molten steel is controlled at 1.89kW / ton of steel, and the nitrogen blowing time is 5min.

[0111] (4) Control the temperature after nitrogen blowing at 1555℃.

[0112] (5) After nitrogen blowing, let the molten steel stand for 0.6 minutes.

[0113] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0065%, there was no slag entrapment, and the steel fluidity was normal. In this example, the final temperature was lower and the nitrogen blowing time was shorter.

[0114] Example 5

[0115] The smelting method for dephosphorization in a converter according to this embodiment includes the following steps:

[0116] (1) Slag formation throughout the converter process.

[0117] (2) The molten steel in the converter is subjected to oxygen blowing smelting. When the oxygen blowing smelting endpoint is reached, the first molten steel is obtained. The endpoint temperature is controlled at 1600℃, the endpoint carbon is controlled at 0.028%, and the endpoint phosphorus is 0.011%.

[0118] (3) Nitrogen blowing is performed on the oxygen lance inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 3.81 m. 3 / min.t; The stirring power density of molten steel is controlled at 1.89kW / ton of steel, and the nitrogen blowing time is 3.5min.

[0119] (4) Control the temperature after nitrogen blowing at 1565℃.

[0120] (5) After nitrogen blowing, let the molten steel stand for 0.8 minutes.

[0121] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0075%, there was no slag entrapment, and the steel fluidity was normal.

[0122] Example 6

[0123] The smelting method for dephosphorization in a converter according to this embodiment includes the following steps:

[0124] (1) Slag formation throughout the converter process.

[0125] (2) The molten steel in the converter is subjected to oxygen blowing smelting. The oxygen blowing smelting endpoint is reached to obtain the first molten steel. The endpoint temperature is controlled at 1625℃, the endpoint carbon is controlled at 0.045%, and the endpoint phosphorus is 0.0142%.

[0126] (3) Nitrogen blowing is performed using oxygen lances inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 4.29 m. 3 / min.t; The stirring power density of molten steel is controlled at 2.13kW / ton of steel, and the nitrogen blowing time is 7min.

[0127] (4) Control the temperature after nitrogen blowing at 1555℃.

[0128] (5) After the nitrogen blowing is completed, let the molten steel stand for 1.2 minutes.

[0129] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0080%, no slag entrapment occurred in the later stage of tapping, and the tapping was normal.

[0130] Example 7

[0131] The smelting method for dephosphorization in a converter according to this embodiment includes the following steps:

[0132] (1) Slag formation throughout the converter process.

[0133] (2) The molten steel in the converter is subjected to oxygen blowing smelting. The first molten steel is obtained when the oxygen blowing smelting endpoint is reached. The endpoint temperature is controlled at 1603℃, the endpoint carbon is controlled at 0.032%, and the endpoint phosphorus is 0.0112%.

[0134] (3) Nitrogen blowing from the oxygen lance inside the converter; the lance position is maintained at 2.5 meters for the first 0-2 minutes of nitrogen blowing, and then adjusted to 1.8 meters for the next 2-7 minutes; the nitrogen blowing intensity is 3.81m. 3 / min.t; The stirring power density of molten steel is controlled at 1.89kW / ton of steel, and the nitrogen blowing time is 4min.

[0135] (4) Control the temperature after nitrogen blowing at 1560℃.

[0136] (5) After the nitrogen blowing is completed, let the molten steel stand for 1.6 minutes.

[0137] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0072%, and no slag entrapment occurred in the later stage of tapping, indicating normal tapping.

[0138] Comparative Example 1

[0139] This comparative example describes a smelting method for dephosphorization in a converter, comprising the following operational steps:

[0140] (1) Slag formation throughout the converter process.

[0141] (2) The molten steel in the converter is subjected to oxygen blowing smelting. The first molten steel is obtained when the oxygen blowing smelting endpoint is reached. The endpoint temperature is controlled at 1650℃, the endpoint carbon is controlled at 0.041%, and the endpoint phosphorus is 0.0165%.

[0142] (3) Nitrogen blowing is performed using oxygen lances inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 2.86 m. 3 / min.t; The stirring power density of molten steel is controlled at 1.42kW / ton of steel, and the nitrogen blowing time is 6min.

[0143] (4) Control the temperature after nitrogen blowing at 1601℃.

[0144] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0121%, which was higher than the standard value. Slight slag entrainment occurred in the later stages of tapping, and the steel was left to run. Due to the high phosphorus content at the tap, the steel was refining.

[0145] Comparative Example 2

[0146] This comparative example describes a smelting method for dephosphorization in a converter, comprising the following operational steps:

[0147] (1) Slag formation throughout the converter process.

[0148] (2) The molten steel in the converter is subjected to oxygen blowing smelting. The first molten steel is obtained when the oxygen blowing smelting endpoint is reached. The endpoint temperature is controlled at 1570℃, the endpoint carbon is controlled at 0.049%, and the endpoint phosphorus of the converter is 0.011%.

[0149] (3) Nitrogen blowing is performed using oxygen lances inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 2.38 m. 3 / min.t; The stirring power density of molten steel is controlled at 1.18kW / ton of steel, and the nitrogen blowing time is 6min.

[0150] (4) Control the temperature after nitrogen blowing at 1533℃.

[0151] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0089%. Due to the excessively low temperature during tapping, severe slag inclusions occurred, and nodules formed at the tapping spout, resulting in incomplete tapping of the steel and necessitating a change in steel grade. In this comparative example, the oxygen blowing smelting endpoint temperature was too low, and nitrogen blowing continued. Although the phosphorus content was reduced to within the standard value at the endpoint, the excessively low temperature led to slag inclusions and incomplete tapping of the steel, resulting in quality and production accidents.

[0152] Comparative Example 3

[0153] This comparative example describes a smelting method for dephosphorization in a converter, comprising the following operational steps:

[0154] (1) Slag formation throughout the converter process.

[0155] (2) The molten steel in the converter is subjected to oxygen blowing smelting. When the oxygen blowing smelting endpoint is reached, the first molten steel is obtained. The endpoint temperature is controlled at 1630℃, the endpoint carbon is controlled at 0.06%, and the endpoint phosphorus is 0.0181%.

[0156] (3) Nitrogen blowing is performed on the oxygen lance inside the converter; the lance position is maintained at 2 meters; the nitrogen blowing intensity is 3.81 m. 3 / min.t; The stirring power density of molten steel is controlled at 1.89kW / ton of steel, and the nitrogen blowing time is 7min.

[0157] (4) Control the temperature after nitrogen blowing at 1570℃.

[0158] (5) After the nitrogen blowing is completed, let the molten steel stand for 1 minute.

[0159] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0146%, which was higher than the standard value. However, the phosphorus content was normal in the later stages of tapping. In this comparative example, the endpoint carbon content was too high, the slag fluidity was poor, and the oxidizing properties were insufficient. The subsequent stirring and dephosphorization were also poor, failing to achieve the target effect.

[0160] Comparative Example 4

[0161] This comparative example describes a smelting method for dephosphorization in a converter, comprising the following operational steps:

[0162] (1) Slag formation throughout the converter process.

[0163] (2) The molten steel in the converter is subjected to oxygen blowing smelting. When the oxygen blowing smelting endpoint is reached, the first molten steel is obtained. The endpoint temperature is controlled at 1622℃, the endpoint carbon is controlled at 0.03%, and the endpoint phosphorus is 0.0142%.

[0164] (3) Nitrogen blowing is performed on the oxygen lance inside the converter; the lance position is maintained at 2.8 meters; the nitrogen blowing intensity is 2.86 m. 3 / min.t; The stirring power density of molten steel is controlled at 1.13kW / ton of steel, and the nitrogen blowing time is 7min.

[0165] (4) Control the temperature after nitrogen blowing at 1586℃.

[0166] Test results: After nitrogen blowing, the phosphorus content of the converter steel was 0.0106%, which was higher than the standard value. Slag was trapped in the molten steel during the later stages of tapping, requiring continued operation with the molten steel remaining. In this comparative example, the lance position was too high, the nitrogen flow rate was too low, the impact energy was poor, and the dephosphorization effect was weak.

[0167] Through the detailed operating steps and parameter control described above, efficient dephosphorization after oxygen blowing in the converter was successfully achieved in actual production. The phosphorus content of the molten steel was stably controlled below 0.01%, resulting in the stable production of ultra-low phosphorus steel. This effectively solved the problems existing in traditional processes and improved the economic efficiency and product quality of steel production. In practical applications, the above parameters can be appropriately adjusted and optimized according to different converter capacities, raw material conditions, and product requirements to ensure the wide applicability and effectiveness of the method of this invention.

[0168] The above are merely specific embodiments of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A smelting method for dephosphorization in a converter, characterized in that, Includes the following steps: The molten steel in the converter is subjected to oxygen blowing smelting. When the oxygen blowing smelting reaches the end point, the first molten steel is obtained. The carbon content of the first molten steel is 0.02%-0.05%, and the temperature of the first molten steel is 1580℃-1630℃. The oxygen blowing is switched to nitrogen blowing, and the first molten steel is smelted by nitrogen blowing. After the molten steel in the converter reaches the preset temperature, the nitrogen blowing smelting endpoint is reached, and converter molten steel is obtained. The preset temperature is 1550℃-1570℃. During nitrogen blowing, the position of the oxygen lance is dynamically adjusted according to the blowing time: for the initial 0-2 minutes, the oxygen lance position is maintained at 2.0-2.5 meters, then adjusted to 1.5-2.0 meters; the blowing intensity is 3.57-4.76 m. 3 / (min.t); During nitrogen blowing, the stirring power density of molten steel is controlled at 1.89-2.36kW / ton of steel to enhance the reaction between molten steel and slag; The nitrogen blowing time is determined according to the temperature difference between the first molten steel and the preset temperature: when the temperature difference is 30-80℃, the nitrogen blowing time is 2-8 minutes; After nitrogen blowing, the molten steel is allowed to stand for 0.5-2 minutes; During the converter smelting process, slag formation is controlled so that the final slag has dephosphorization capability, and the phosphorus content of the converter molten steel is ≤0.01%.