Desulfurization method for RH refined molten steel

Abstract

The invention provides a method for desulfurizing RH refined molten steel, and belongs to the field of steel smelting. The method comprises the following steps: after molten steel deoxidation alloying in an RH refining process is finished, carrying out first vacuum circulation on the molten steel; a first batch of desulfurizing agent is added into the molten steel subjected to the first vacuum circulation, and argon top blowing is carried out; within a set time interval after the first batch of desulfurizing agent is added, a second batch of desulfurizing agent is added into the molten steel, and then second vacuum circulation is conducted; and the molten steel subjected to the second vacuum circulation is subjected to vacuum breaking, and top blowing of argon is ended. Through top blowing of argon, melting of the desulfurizing agent is promoted, and good dynamic conditions are created for reaction of the desulfurizing agent and molten steel in the RH vacuum chamber, so that the utilization rate and desulfurization efficiency of the desulfurizing agent are improved, and the method has important significance in control of the sulfur content of an ultra-low carbon steel finished product.

Description

Technical Field

[0001] This application relates to the technical field of steel smelting, and particularly to a method for desulfurizing molten steel in RH refining. Background Art

[0002] Sulfur is a harmful element for the vast majority of steel grades, and the presence of sulfur will increase the risk of hot brittleness of steel. Therefore, desulfurization has always been an important task in the steel metallurgy process. At present, the common desulfurization means in the steel manufacturing process include hot metal pretreatment process and LF refining process; among them, the LF refining process is used for desulfurizing molten steel. Since the quality of molten steel directly affects the quality of the final steel, domestic and foreign metallurgical scholars pay more attention to LF refining desulfurization. LF refining mainly adopts the method of making a reducing white slag for desulfurization. For ultra-low carbon steel, if LF desulfurization is used, problems such as re-carburization and re-phosphorization of molten steel will occur, which will deteriorate the quality of molten steel instead; in addition, the LF refining treatment cycle is relatively long, which is not conducive to the efficient production of the steelmaking process.

[0003] In order to solve the problem of desulfurization of ultra-low carbon steel, domestic and foreign steel enterprises have tried to carry out desulfurization in the RH refining process. RH refining is a necessary process for producing ultra-low carbon steel. Therefore, simultaneously completing the tasks of decarburization and desulfurization in the RH refining process is one of the important research directions explored by metallurgical workers. At present, the main methods for RH refining desulfurization are the injection method and the powder injection method. The injection method is simple to operate, but the utilization rate of desulfurizer is low; the utilization rate of desulfurizer in the powder injection method is relatively high, but it has high requirements for factors such as the particle size of the desulfurizer. If the control is improper, problems such as lance blockage are likely to occur, and the equipment stability and maintenance difficulty are relatively large. Therefore, how to improve the utilization rate of desulfurizer and desulfurization efficiency is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0004] This application provides a method for desulfurizing molten steel in RH refining to solve the following technical problems: how to improve the utilization rate of desulfurizer and desulfurization efficiency.

[0005] An embodiment of this application provides a method for desulfurizing molten steel in RH refining, and the method includes:

[0006] After the deoxidation and alloying of molten steel in the RH refining process are completed, perform the first vacuum circulation on the molten steel;

[0007] Add the first batch of desulfurizer to the molten steel after the first vacuum circulation, and perform top blowing of argon;

[0008] Within a set time interval after adding the first batch of desulfurizer, add the second batch of desulfurizer to the molten steel, and then perform the second vacuum circulation; and

[0009] Break the vacuum of the molten steel after the second vacuum circulation, and end the top blowing of argon.

[0010] Optionally, the time of the first vacuum cycle is 1 min to 2 min, and the lifting gas flow rate of the first vacuum cycle is 2400 NL / min to 2600 NL / min.

[0011] Optionally, the total addition amount of the first batch of desulfurizer and the second batch of desulfurizer is 6.5 kg / t steel to 7.0 kg / t steel.

[0012] Optionally, by mass fraction, the desulfurizer comprises the following chemical components: CaO: 50% to 55%, Al2O3: 20% to 25%, CaF2: 10% to 15%, MgO: 2% to 4%, SiO2 ≤ 6%.

[0013] Optionally, the mass of the first batch of desulfurizer is 50% to 60% of the total mass of the desulfurizer, and the mass of the second batch of desulfurizer is 40% to 50% of the total mass of the desulfurizer.

[0014] Optionally, the lance position height of the RH top lance for top-blowing argon is 1.8 m to 2.0 m.

[0015] Optionally, the argon blowing flow rate for top-blowing argon is 2500 NL / min to 3000 NL / min.

[0016] Optionally, the set time interval is 1 min to 2 min.

[0017] Optionally, the time of the second vacuum cycle is 4 min to 6 min, and the lifting gas flow rate of the second vacuum cycle is 2400 NL / min to 2600 NL / min.

[0018] Optionally, by mass fraction, the S content in the molten steel at the end of RH refining is ≤ 0.0015%, and the desulfurization rate of RH refining is ≥ 60%.

[0019] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0020] The embodiment of the present application provides a method for desulfurizing molten steel in RH refining. First, after the deoxidation and alloying of molten steel are completed during RH refining, the first vacuum cycle is used to promote the full dissolution of alloying agents, creating good thermodynamic conditions for desulfurization. Secondly, by adding desulfurizing agents in batches, it can ensure the continuous reaction of desulfurizing agents in molten steel, avoiding problems such as agglomeration and insufficient reaction caused by adding too much desulfurizing agent at one time, thereby improving the utilization rate of desulfurizing agents. Thirdly, by top-blowing argon, it promotes the melting of desulfurizing agents and creates good kinetic conditions for the reaction between desulfurizing agents and molten steel in the RH vacuum chamber. Finally, through the second vacuum cycle, the desulfurization reaction is promoted, enabling the desulfurizing agent to react more fully with sulfur in molten steel. Thus, the utilization rate of desulfurizing agents and desulfurization efficiency are improved, which is of great significance for controlling the sulfur content of ultra-low carbon steel finished products. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic flow chart of a method for desulfurizing molten steel in RH refining provided by the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described examples are some, but not all, of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0025] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0026] In addition, in the description of the specification of the present application, terms such as "including" and "comprising" mean "including but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may indicate: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B may be singular or plural. In this text, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively. The "parts representation method" such as parts by weight and parts by mass represents the proportional relationship between each component. In the proportional relationships involved in this text, the parameters that need to be described by proportion should be understood as the antecedents of the proportional formula in the order of description, and the proportional numbers should be understood as the consequents of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond to the proportional numbers in the proportional formula one by one in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0027] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present application can be obtained through market purchase or can be prepared by existing methods.

[0028] Figure 1 It is a schematic flow diagram of a method for desulfurizing molten steel in RH refining provided for the embodiments of the present application.

[0029] like Figure 1 As shown, the present application provides a method for desulfurization of RH refined molten steel, the method comprising:

[0030] S1. After the deoxidation and alloying of the molten steel in the RH refining process is completed, the molten steel is subjected to a first vacuum cycle;

[0031] It should be noted that during the RH refining of molten steel, vacuum circulation is carried out until the air is broken. The time of the first vacuum cycle is 1min to 2min, which means that the interval from the end of deoxidation and alloying to the addition of desulfurization agent is 1min to 2min. The first vacuum cycle promotes the full dissolution of alloying agents such as ferrosilicon. The more fully the alloy is dissolved, the more conducive it is to the increase of sulfur activity in molten steel, creating a more favorable environment for the subsequent desulfurization reaction.

[0032] In some embodiments, the amount of alloy added for deoxidation alloying is determined according to the upper limit of Si and Al content in the finished steel. According to metallurgical thermodynamics theory, the higher the [Si] and [Al] content in molten steel, the higher the activity of [S] in the molten steel, which is more conducive to the desulfurization reaction.

[0033] In some embodiments, the duration of the first vacuum cycle is 1 min to 2 min, and the lifting gas flow rate of the first vacuum cycle is 2400 NL / min to 2600 NL / min.

[0034] After alloying, the vacuum cycle is 1min to 2min, and the lifting gas flow rate is 2400NL / min to 2600NL / min to ensure the full dissolution of the alloying agent and create good thermodynamic conditions for desulfurization. Exemplarily, the time of the first vacuum cycle can be 1min, 1.2min, 1.4min, 1.6min, 1.8min, 2min, etc., and the lifting gas flow rate of the first vacuum cycle can be 2400NL / min, 2450NL / min, 2500NL / min, 2550NL / min, 2600NL / min, etc.

[0035] S2, adding the first batch of desulfurizer to the molten steel after the first vacuum cycle, and top blowing argon;

[0036] Argon is used as a driving gas and introduced into the molten steel by top blowing to form a jet and stir the molten steel, thereby promoting full contact and reaction between the desulfurizer and the molten steel.

[0037] S3, adding a second batch of desulfurizer to the molten steel within a set time interval after adding the first batch of desulfurizer, and then performing a second vacuum cycle;

[0038] In some embodiments, the total addition amount of the first batch of desulfurizer and the second batch of desulfurizer is 6.5 kg / t steel to 7.0 kg / t steel.

[0039] Limiting the total addition amount of the desulfurizer to 6.5 kg / t steel to 7.0 kg / t steel can optimize the desulfurization effect, improve the quality of molten steel and the stability of the refining process. Exemplarily, the total addition amount of the desulfurizer is 6.5 kg / t steel, 6.6 kg / t steel, 6.7 kg / t steel, 6.8 kg / t steel, 6.9 kg / t steel, 7.0 kg / t steel, etc.

[0040] In some embodiments, by mass fraction, the desulfurizer comprises the following chemical components: CaO: 50% - 55%, Al2O3: 20% - 25%, CaF2: 10% - 15%, MgO: 2% - 4%, SiO2 ≤ 6%.

[0041] In the embodiments of the present application, through thermodynamic and kinetic calculations, a desulfurizer formula with high sulfur capacity and low apparent viscosity is designed, and the erosion problem of the immersion tube is alleviated by controlling the content of CaF2. Specifically, the functions of the chemical components in the desulfurizer are as follows:

[0042] CaO: CaO is the main active component in the desulfurizer. It reacts with sulfur in the molten steel to form calcium sulfide (CaS), thereby achieving desulfurization. Within this range, the content of CaO is high enough to ensure an effective desulfurization reaction. At the same time, an appropriate content of CaO also helps to increase the melting point and stability of the desulfurizer, preventing it from decomposing or volatilizing prematurely at high temperatures. Exemplarily, the mass fraction of CaO can be 50%, 51%, 52%, 53%, 54%, 55%, etc.

[0043] Al2O3: An appropriate amount of Al2O3 can improve the fluidity of the refining slag and assist in deoxidation to promote desulfurization. Exemplarily, the mass fraction of Al2O3 can be 20%, 21%, 22%, 23%, 24%, 25%, etc.

[0044] CaF2: CaF2 mainly plays the role of reducing the melting point and improving the fluidity in the desulfurizer. It can significantly reduce the melting point of the desulfurizer, enabling it to react fully with the molten steel at a lower temperature. At the same time, CaF2 can also improve the fluidity of the desulfurizer, making it easier to disperse and react in the molten steel. Exemplarily, the mass fraction of CaF2 can be 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0045] MgO: An appropriate amount of MgO can increase the basicity, sulfur capacity and fluidity of the slag, directly participate in the desulfurization reaction, and protect the refractory materials. Exemplarily, the mass fraction of MgO can be 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0046] SiO2: In the desulfurizer, SiO2 mainly plays the role of regulating the melting point and viscosity. An appropriate amount of SiO2 can reduce the melting point of the desulfurizer and improve its fluidity. However, too high a content of SiO2 will cause an increase in the viscosity of the desulfurizer, which is not conducive to its dispersion and reaction in the molten steel. Therefore, controlling the content of SiO2 within the range of ≤6% can ensure that the desulfurizer has good fluidity and reactivity. Exemplarily, the mass fraction of SiO2 can be 1%, 2%, 3%, 4%, 5%, 6%, etc.

[0047] In some embodiments, the mass of the first batch of desulfurizer is 50% - 60% of the total mass of the desulfurizer, and the mass of the second batch of desulfurizer is 40% - 50% of the total mass of the desulfurizer.

[0048] The addition amount of the first batch of desulfurizer is relatively large (50% - 60% of the total mass of the desulfurizer) because it is added 1 - 2 minutes earlier than the second batch of desulfurizer and has a relatively longer desulfurization time. An appropriate amount of desulfurizer can improve the desulfurization efficiency, but too much desulfurizer may cause agglomeration, which will instead affect the utilization rate. The addition amount of the second batch of desulfurizer is 40% - 50% of the total mass of the desulfurizer. Appropriately supplementing the desulfurizer can further improve the desulfurization efficiency. Exemplarily, the mass of the first batch of desulfurizer can be 50%, 52%, 54%, 56%, 58%, 60%, etc. of the total mass of the desulfurizer, and the mass of the second batch of desulfurizer can be 40%, 42%, 44%, 46%, 48%, 50%, etc. of the total mass of the desulfurizer.

[0049] In some embodiments, the set time interval is 1 min - 2 min.

[0050] An interval of 1 - 2 minutes allows the first batch of desulfurizer to react preliminarily with the molten steel, and at the same time provides a better reaction environment for the subsequent added desulfurizer, which helps to ensure the continuity and high efficiency of the desulfurization reaction. Exemplarily, the time interval between the first batch of desulfurizer and the second batch of desulfurizer is 1 min, 1.2 min, 1.4 min, 1.6 min, 1.8 min, 2 min, etc.

[0051] In some embodiments, the time of the second vacuum cycle is 4 min - 6 min, and the lifting gas flow rate of the second vacuum cycle is 2400 NL / min - 2600 NL / min.

[0052] A cycle time of 4 - 6 minutes allows the desulfurization reaction to proceed fully. Meanwhile, a lifting gas flow rate of 2400 NL / min - 2600 NL / min can ensure sufficient agitation of the molten steel and uniform distribution of the desulfurizing agent, thereby improving the desulfurization efficiency. Exemplarily, the time of the second vacuum cycle can be 4 min, 4.5 min, 5 min, 5.5 min, 6 min, etc., and the lifting gas flow rate can be 2400 NL / min, 2450 NL / min, 2500 NL / min, 2550 NL / min, 2600 NL / min, etc.

[0053] In some embodiments, the lance height of the RH top lance with argon top blowing is 1.8 m - 2.0 m.

[0054] Defining the lance height of the RH top lance to be 1.8 - 2.0 m can give full play to its impact on the molten bath by optimizing the gas flow, improve the desulfurization efficiency and quality, protect the equipment and extend its service life, and enhance the stability and controllability of the refining process. If the lance position is too high, the impact of the gas flow on the molten bath in the vacuum chamber is weak, and the improvement of desulfurization kinetics conditions is limited; if the lance position is too low, the impact of the gas flow on the molten bath in the vacuum chamber is strong, and the splashed slag and steel are likely to cause problems such as gun sticking, affecting the use of the equipment. Exemplarily, the lance height of the RH top lance with argon top blowing can be 1.8 m, 1.85 m, 1.9 m, 1.95 m, 2.0 m, etc.

[0055] In some embodiments, the argon blowing flow rate of the argon top blowing is 2500 NL / min - 3000 NL / min.

[0056] Defining the argon blowing flow rate to be 2500 NL / min - 3000 NL / min can give full play to its agitation of the molten bath and promotion of the desulfurization reaction. If the argon blowing flow rate is lower than 2500 NL / min, the impact of the gas flow on the molten bath in the vacuum chamber is weak, and the improvement of desulfurization kinetics conditions is limited; if the argon blowing flow rate is higher than 3000 NL / min, the impact of the gas flow on the molten bath in the vacuum chamber is strong, and the splashed slag and steel are likely to cause problems such as gun sticking, affecting the use of the equipment. Exemplarily, the argon blowing flow rate of the argon top blowing can be 2500 NL / min, 2600 NL / min, 2700 NL / min, 2800 NL / min, 2900 NL / min, 3000 NL / min, etc.

[0057] S4. Break the vacuum of the molten steel after the second vacuum cycle and end the argon top blowing.

[0058] Breaking the vacuum means ending the vacuum state and restoring normal pressure, preparing for subsequent processes such as casting.

[0059] In some embodiments, by mass fraction, the S content in the molten steel at the end of RH refining is ≤ 0.0015%, and the desulfurization rate of RH refining is ≥ 60%.

[0060] In the embodiments of the present application, by top-blowing argon, the melting of the desulfurizer is promoted, and good kinetic conditions are created for the reaction between the desulfurizer and the molten steel in the RH vacuum chamber, improving the utilization rate and desulfurization efficiency of the desulfurizer. Exemplarily, the S content in the molten steel at the end of RH refining can be 0.0008%, 0.0009%, 0.0011%, 0.0012%, 0.0014%, 0.0015%, etc., and the desulfurization rate of RH refining can be 60%, 61%, 62%, 64%, 66%, 68%, 70%, etc.

[0061] In summary, a method for desulfurizing molten steel by RH refining provided by the embodiments of the present application has the following advantages:

[0062] (1) High-efficiency desulfurization: By precisely controlling the composition and addition amount of the desulfurizer (6.5 kg / t steel - 7.0 kg / t steel), and the strategy of adding the desulfurizer in batches, the efficient progress of the desulfurization reaction is ensured. At the same time, the high content of CaO in the desulfurizer guarantees effective desulfurization activity, while other components such as Al2O3, CaF2, MgO, and SiO2 play multiple roles such as promoting melting, stabilizing, reducing the melting point, and adjusting viscosity, jointly optimizing the desulfurization effect.

[0063] (2) Optimizing thermodynamic conditions: The first vacuum cycle (1 min - 2 min) carried out after deoxidation alloying promotes the full dissolution of alloying agents such as ferrosilicon, creating a more favorable environment for the desulfurization reaction. When alloying, the addition amount of the alloy is determined according to the upper limit of the finished Si and Al contents of the steel grade, increasing the activity of [S] in the molten steel and facilitating the progress of the desulfurization reaction.

[0064] (3) Good kinetic conditions: The lance position height of the RH top lance with top-blowing argon is controlled at 1.8 m - 2.0 m, optimizing the impact of the gas flow on the molten pool and improving the desulfurization efficiency and quality. The argon blowing flow rate is limited to 2500 NL / min - 3000 NL / min, which not only ensures sufficient agitation of the molten pool but also avoids problems such as slag-steel splashing and gun sticking.

[0065] (4) Stable and controllable refining process: By precisely controlling the time interval (1 min - 2 min) between the addition of the first batch and the second batch of desulfurizer, the time (4 min - 6 min) of the second vacuum cycle, and the lifting gas flow rate (2400 NL / min - 2600 NL / min), the stability and controllability of the refining process are ensured. The selection of reasonable operating parameters helps to reduce uncertain factors during the refining process, improving production efficiency and product quality.

[0066] (5) High-quality molten steel: After the refining is completed, the S content in the molten steel can be as low as below 0.0015%, and the desulfurization rate can reach over 60%, meeting the production requirements of high-quality molten steel. The refining process also helps to reduce the oxygen content and other impurity contents in the molten steel, improving the purity and uniformity of the molten steel.

[0067] (6) Equipment protection and extended service life: The selection of reasonable operating parameters reduces the occurrence of problems such as equipment wear and gun sticking, helping to protect the RH equipment and extend its service life.

[0068] The following will further elaborate on this application in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. For the experimental methods without specific conditions indicated in the following embodiments, they are usually determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0069] The following examples and comparative examples are all for RH refining desulfurization of a certain grade of non-oriented silicon steel.

[0070] Example 1

[0071] 1) After the deoxidation alloying of the molten steel in the RH refining process is completed, vacuum circulation is carried out for 1 min, the lifting gas flow rate is controlled at 2500 NL / min, and then the desulfurizing agent is started to be added;

[0072] 2) The desulfurizing agent is added in two batches, with an interval of 1 min between the two batches. The total amount of desulfurizing agent added is controlled at 6.5 kg / t of steel. The addition amount of the first batch of desulfurizing agent is controlled at 50 wt% of the total amount, and the addition amount of the second batch of desulfurizing agent is controlled at 50 wt% of the total amount;

[0073] 3) The main components of the desulfurizing agent are CaO: 50 wt%, Al2O3: 25 wt%, CaF2: 15 wt%, MgO: 4 wt%, SiO2: 6 wt%;

[0074] 4) After the second batch of desulfurizing agent is added, circulation is carried out for 4 min, the lifting gas flow rate is controlled at 2500 NL / min, and then the vacuum is broken;

[0075] 5) When the first batch of desulfurizing agent is added, the RH top lance is used to blow argon, the lance position of the top lance is controlled at 1.8 m, and the argon blowing flow rate is controlled at 2500 NL / min;

[0076] 6) When the vacuum is broken, the RH top lance stops blowing argon.

[0077] Example 2

[0078] 1) After the deoxidation and alloying of molten steel in the RH refining process, the vacuum cycle is carried out for 1.5 minutes, the gas flow rate is controlled at 2500NL / min, and then the desulfurizer is added;

[0079] 2) The desulfurizer is added in two batches, with an interval of 1.5 minutes between the two batches. The total amount of desulfurizer added is controlled at 6.8 kg / t steel. The amount of the first batch of desulfurizer added is controlled at 55 wt% of the total amount, and the amount of the second batch of desulfurizer added is controlled at 45 wt% of the total amount;

[0080] 3) The main components of the desulfurizer are CaO: 55wt%, Al2O3: 22wt%, CaF2: 15wt%, MgO: 2wt%, SiO2: 6wt%;

[0081] 4) After the second batch of desulfurizer is added, circulate for 5 minutes, increase the gas flow rate to 2500NL / min, and then break the air;

[0082] 5) When the first batch of desulfurizer is added, the RH top gun is turned on to spray argon. The gun position of the top gun is controlled at 1.9m, and the argon spray flow rate is controlled at 2800NL / min.

[0083] 6) At the same time as the air is broken, the RH top gun stops blowing argon.

[0084] Example 3

[0085] 1) After the deoxidation and alloying of molten steel in the RH refining process, the vacuum cycle is carried out for 2 minutes, the gas flow rate is controlled at 2500NL / min, and then the desulfurizer is added;

[0086] 2) The desulfurizer is added in two batches, with an interval of 2 minutes between the two batches. The total amount of desulfurizer added is controlled at 7kg / t steel. The amount of the first batch of desulfurizer added is controlled at 60wt% of the total amount, and the amount of the second batch of desulfurizer added is controlled at 40wt% of the total amount;

[0087] 3) The main components of the desulfurizer are CaO: 52wt%, Al2O3: 25wt%, CaF2: 13wt%, MgO: 4wt%, SiO2: 6wt%;

[0088] 4) After the second batch of desulfurizer is added, circulate for 6 minutes, increase the gas flow rate to control at 2500NL / min, and then break the air;

[0089] 5) When the first batch of desulfurizer is added, the RH top gun is turned on to spray argon. The gun position of the top gun is controlled at 2.0m, and the argon spray flow rate is controlled at 3000NL / min;

[0090] 6) At the same time as the air is broken, the RH top gun stops blowing argon.

[0091] Comparative Example 1

[0092] 1) After the deoxidation and alloying of molten steel in the RH refining process are completed, a desulfurizing agent is directly added, and the lifting gas flow rate is controlled at 2500 NL / min.

[0093] 2) The desulfurizing agent is added in two batches, with an interval of 1 min between the two batches. The total amount of desulfurizing agent added is controlled at 6.5 kg / t of steel. The amount of the first batch of desulfurizing agent added is controlled at 50 wt% of the total amount, and the amount of the second batch of desulfurizing agent added is controlled at 50 wt% of the total amount.

[0094] 3) The main components of the desulfurizing agent are CaO: 50 wt%, Al2O3: 25 wt%, CaF2: 15 wt%, MgO: 4 wt%, and SiO2: 6 wt%.

[0095] 4) After the second batch of desulfurizing agent is added, it is circulated for 4 min, and the lifting gas flow rate is controlled at 2500 NL / min, and then the vacuum is broken.

[0096] 5) When the first batch of desulfurizing agent is added, the RH top lance is started to blow argon, the lance position of the top lance is controlled at 1.8 m, and the argon blowing flow rate is controlled at 2500 NL / min.

[0097] 6) When the vacuum is broken, the RH top lance stops blowing argon.

[0098] Comparative Example 2

[0099] 1) After the deoxidation and alloying of molten steel in the RH refining process are completed, it is vacuum circulated for 1 min, the lifting gas flow rate is controlled at 2500 NL / min, and then the desulfurizing agent is started to be added.

[0100] 2) The desulfurizing agent is added in two batches, with an interval of 1 min between the two batches. The total amount of desulfurizing agent added is controlled at 6.0 kg / t of steel. The amount of the first batch of desulfurizing agent added is controlled at 50 wt% of the total amount, and the amount of the second batch of desulfurizing agent added is controlled at 50 wt% of the total amount.

[0101] 3) The main components of the desulfurizing agent are CaO: 50 wt%, Al2O3: 25 wt%, CaF2: 15 wt%, MgO: 4 wt%, and SiO2: 6 wt%.

[0102] 4) After the second batch of desulfurizing agent is added, it is circulated for 4 min, the lifting gas flow rate is controlled at 2500 NL / min, and then the vacuum is broken.

[0103] 5) When the first batch of desulfurizing agent is added, the RH top lance is started to blow argon, the lance position of the top lance is controlled at 1.8 m, and the argon blowing flow rate is controlled at 2500 NL / min.

[0104] 6) When the vacuum is broken, the RH top lance stops blowing argon.

[0105] Comparative Example 3

[0106] 1) After the deoxidation and alloying of molten steel in the RH refining process are completed, vacuum circulation is carried out for 1 minute, the lifting gas flow rate is controlled at 2500 NL / min, and then the desulfurizer is started to be added.

[0107] 2) The desulfurizer is added in two batches, with an interval of 1 minute between the two batches. The total amount of desulfurizer added is controlled at 6.5 kg / t of steel. The amount of the first batch of desulfurizer added is controlled at 50 wt% of the total amount, and the amount of the second batch of desulfurizer added is controlled at 50 wt% of the total amount.

[0108] 3) The main components of the desulfurizer are CaO: 45 wt%, Al2O3: 30 wt%, CaF2: 15 wt%, MgO: 4 wt%, SiO2: 6 wt%.

[0109] 4) After the second batch of desulfurizer is added, circulation is carried out for 4 minutes, the lifting gas flow rate is controlled at 2500 NL / min, and then the vacuum is broken.

[0110] 5) When the first batch of desulfurizer is added, the RH top lance is started to blow argon, the lance position of the top lance is controlled at 1.8 m, and the argon blowing flow rate is controlled at 2500 NL / min.

[0111] 6) When the vacuum is broken, the RH top lance stops blowing argon.

[0112] Comparative Example 4

[0113] 1) After the deoxidation and alloying of molten steel in the RH refining process are completed, vacuum circulation is carried out for 1 minute, the lifting gas flow rate is controlled at 2500 NL / min, and then the desulfurizer is started to be added.

[0114] 2) The desulfurizer is added in two batches, with an interval of 1 minute between the two batches. The total amount of desulfurizer added is controlled at 6.5 kg / t of steel. The amount of the first batch of desulfurizer added is controlled at 50 wt% of the total amount, and the amount of the second batch of desulfurizer added is controlled at 50 wt% of the total amount.

[0115] 3) The main components of the desulfurizer are CaO: 50 wt%, Al2O3: 25 wt%, CaF2: 15 wt%, MgO: 4 wt%, SiO2: 6 wt%.

[0116] 4) After the second batch of desulfurizer is added, circulation is carried out for 2 minutes, the lifting gas flow rate is controlled at 2500 NL / min, and then the vacuum is broken.

[0117] 5) When the first batch of desulfurizer is added, the RH top lance is started to blow argon, the lance position of the top lance is controlled at 1.8 m, and the argon blowing flow rate is controlled at 2500 NL / min.

[0118] 6) When the vacuum is broken, the RH top lance stops blowing argon.

[0119] Comparative Example 5

[0120] 1) After the deoxidation alloying of the molten steel in the RH refining process is completed, vacuum circulation is carried out for 1 minute, the lifting gas flow rate is controlled at 2500 NL / min, and then the desulfurizer is started to be added;

[0121] 2) The desulfurizer is added in two batches, with an interval of 1 minute between the two batches. The total amount of desulfurizer added is controlled at 6.5 kg / t of steel. The amount of the first batch of desulfurizer added is controlled at 50 wt% of the total amount, and the amount of the second batch of desulfurizer added is controlled at 50 wt% of the total amount;

[0122] 3) The main components of the desulfurizer are CaO: 50 wt%, Al2O3: 25 wt%, CaF2: 15 wt%, MgO: 4 wt%, SiO2: 6 wt%;

[0123] 4) After the second batch of desulfurizer is added, circulation is carried out for 4 minutes, the lifting gas flow rate is controlled at 2500 NL / min, and then the vacuum is broken;

[0124] 5) While the first batch of desulfurizer is added, the top lance of the RH blows argon gas, the lance position of the top lance is controlled at 1.5 m, and the argon gas blowing flow rate is controlled at 2500 NL / min;

[0125] 6) While the vacuum is broken, the top lance of the RH stops blowing argon gas.

[0126] Comparative Example 6

[0127] 1) After the deoxidation alloying of the molten steel in the RH refining process is completed, vacuum circulation is carried out for 1 minute, the lifting gas flow rate is controlled at 2500 NL / min, and then the desulfurizer is started to be added;

[0128] 2) The desulfurizer is added in two batches, with an interval of 1 minute between the two batches. The total amount of desulfurizer added is controlled at 6.5 kg / t of steel. The amount of the first batch of desulfurizer added is controlled at 50 wt% of the total amount, and the amount of the second batch of desulfurizer added is controlled at 50 wt% of the total amount;

[0129] 3) The main components of the desulfurizer are CaO: 50 wt%, Al2O3: 25 wt%, CaF2: 15 wt%, MgO: 4 wt%, SiO2: 6 wt%;

[0130] 4) After the second batch of desulfurizer is added, circulation is carried out for 5 minutes, the lifting gas flow rate is controlled at 2500 NL / min, and then the vacuum is broken;

[0131] 5) Argon gas is not blown during the desulfurization process.

[0132] The application effect of the method of the present invention is characterized by the [S] content (wt%) of the molten steel at the end of RH refining, the desulfurization rate (%), and the slag adhesion condition of the lance at the end of desulfurization. The results are shown in Table 1. Among them, the desulfurization rate = (the [S] content of the molten steel before refining + the S increase amount of the alloy - the [S] content of the molten steel at the end of refining) * 100 / the [S] content of the molten steel before refining. The judgment criterion for the qualified [S] content of a certain grade of non-oriented silicon steel corresponding to the examples and comparative examples is ≤0.0015%.

[0133] Table 1 Desulfurization performance of RH refining in Examples 1 - 3 and Comparative Examples 1 - 6

[0134] Comparison items Content of molten steel [S] after refining, wt% Desulfurization rate, % Whether the lance is slagged Example 1 0.0015 62.5 No Example 2 0.0013 67.5 No Example 3 0.0013 67.5 No Comparative Example 1 0.0017 57.5 No Comparative Example 2 0.0020 50.0 No Comparative Example 3 0.0022 45.0 No Comparative Example 4 0.0020 50.0 No Comparative Example 5 0.0012 70.0 Yes Comparative Example 6 0.0018 55.0 No

[0135] As can be seen from Table 1, for the method of desulfurizing molten steel by RH refining provided in Examples 1 - 3, the [S] content of the molten steel at the end of refining is controlled within 0.0015%, the desulfurization rate is not less than 60%, and there is no slag adhesion on the lance. In Comparative Example 1, after the deoxidation alloying of the molten steel was completed, the desulfurizer was added without waiting for the alloying agent to dissolve sufficiently, which affected the thermodynamic conditions in the initial desulfurization stage and the desulfurization rate decreased; in Comparative Example 2, the total amount of desulfurizer added was less than 6.5 kg / t of steel, and the desulfurization rate decreased; in Comparative Example 3, the chemical composition of the desulfurizer did not meet the requirements, and the desulfurization rate decreased; in Comparative Example 4, the vacuum circulation time after the addition of the second batch of desulfurizer was less than 4 min, and the desulfurization rate decreased; in Comparative Example 5, the lance position height of the top blowing argon was less than 1.8 m, and there was slag adhesion on the lance; in Comparative Example 6, no top blowing argon was carried out, and the desulfurization rate decreased.

[0136] In addition, one or more technical solutions in the embodiments of the present application at least further have the following technical effects or advantages:

[0137] In the embodiments of the present application, the [S] content of the molten steel at the end of refining is controlled within 0.0015%, the desulfurization rate is not less than 60%, and there is no slag adhesion on the lance.

[0138] In the embodiments of the present application, the top blowing argon improves the kinetic conditions of the input method for desulfurization, improves the utilization rate of the desulfurizer, the top lance only blows gas without injecting powder, avoiding the problem of lance blockage and improving the equipment stability.

[0139] In the embodiments of the present application, through thermodynamic and kinetic calculations, a desulfurizer formula with high sulfur capacity and low apparent viscosity is designed, and by controlling the CaF2 content, the erosion problem of the immersion tube is alleviated.

[0140] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for desulfurizing molten steel in RH refining, the method comprising: After the deoxidation alloying of the molten steel is completed during RH refining, performing a first vacuum cycle on the molten steel; Adding a first batch of desulfurizing agent to the molten steel after the first vacuum cycle, and blowing argon from the top; Adding a second batch of desulfurizing agent to the molten steel within a set time interval after adding the first batch of desulfurizing agent, and then performing a second vacuum cycle; And Breaking the vacuum of the molten steel after the second vacuum cycle, and ending the argon blowing from the top.

2. The method according to claim 1, wherein The time of the first vacuum cycle is 1 min to 2 min, and the lifting gas flow rate of the first vacuum cycle is 2400 NL / min to 2600 NL / min.

3. The method according to claim 1, characterized in that, The total amount of the first batch of desulfurizing agent and the second batch of desulfurizing agent added is 6.5 kg / t of molten steel to 7.0 kg / t of molten steel.

4. The method according to claim 3, characterized in that By mass fraction, the desulfurizing agent comprises the following chemical components: CaO: 50% - 55%, Al2O3: 20% - 25%, CaF2: 10% - 15%, MgO: 2% - 4%, SiO2 ≤ 6%.

5. The method according to claim 3, wherein The mass of the first batch of desulfurizing agent is 50% - 60% of the total mass of the desulfurizing agent, and the mass of the second batch of desulfurizing agent is 40% - 50% of the total mass of the desulfurizing agent.

6. The method according to claim 1, characterized in that The height of the RH top lance for blowing argon from the top is 1.8 m to 2.0 m.

7. The method according to claim 1, characterized in that, The argon blowing flow rate for blowing argon from the top is 2500 NL / min to 3000 NL / min.

8. The method according to claim 1, characterized in that The set time interval is 1 min to 2 min.

9. The method according to claim 1, wherein The time of the second vacuum cycle is 4 min to 6 min, and the lifting gas flow rate of the second vacuum cycle is 2400 NL / min to 2600 NL / min.

10. The method according to claim 1, characterized in that, By mass fraction, the S content in the molten steel at the end of RH refining is ≤ 0.0015%, and the desulfurization rate of RH refining is ≥ 60%.

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