RH refining oxygen blowing decarburization method

Abstract

The invention belongs to the field of ferrous metallurgy, and discloses an RH refining oxygen blowing decarburization method which comprises the following steps: dynamically adjusting the oxygen blowing flow and the oxygen blowing lance position according to the ratio of the content of carbon to the content of oxygen in RH incoming steel; the oxygen blowing amount is determined according to the initial values of the carbon and oxygen contents in the RH entering steel and the target values of the carbon and oxygen contents after decarburization is finished; a gradient lifting gas flow system is adopted in the RH decarburization process, the oxygen blowing opportunity of RH decarburization and the vacuum pressure in the oxygen blowing process are controlled, and when RH decarburization is finished, molten steel is controlled to be low in oxygen activity. According to different RH entering molten steel components, the oxygen blowing flow and the oxygen blowing lance position are dynamically adjusted, the gradient gas flow increasing system is adopted, the RH decarburization oxygen blowing opportunity, the oxygen blowing process vacuum pressure and decarburization ending molten steel oxygen activity control are combined, the oxygen utilization rate can be effectively increased, the decarburization period is shortened, and the decarburization efficiency is improved. The problem of molten steel recarburization caused by molten steel splashing due to too violent carbon-oxygen reaction is solved, RH efficient decarburization is achieved, the steel ladle top slag oxidability is reduced, and the molten steel cleanliness is improved.

Description

Technical Field

[0001] The present invention relates to the field of iron and steel metallurgy, and in particular to a method for RH refining oxygen blowing decarburization. Background Art

[0002] With the rapid development of the new energy vehicle industry, the demand for ultra-low carbon IF steel (interstitial-free steel) is increasing. The use of RH (RH-vacuum degassing is a steel liquid vacuum treatment technology, jointly developed by the Ruhrstah Steel Company and Heraeus Company in the Federal Republic of Germany in 1956, so it is named RH vacuum degassing method after the initials of the two companies, referred to as RH method) refining equipment for vacuum decarburization is an important way to achieve ultra-low carbon content in IF steel. If the RH inlet oxygen content is not enough to remove the carbon in the steel, the RH vacuum oxygen blowing decarburization method is required, that is, the oxygen content in the steel is increased by blowing oxygen into the molten steel in the vacuum chamber through the top gun to quickly remove the carbon in the steel. At present, when RH refining uses vacuum oxygen blowing decarburization process to produce IF steel, fixed oxygen blowing flow rate and oxygen blowing gun position are usually used under different RH inlet steel liquid components, as well as an inappropriate gas flow rate increase system, which will cause the carbon-oxygen reaction to be too intense, causing serious splashing of the molten steel, thereby causing the problem of carbon increase in the molten steel and low oxygen utilization rate in the oxygen blowing process, making it difficult to improve the decarburization efficiency.

[0003] On the other hand, if the oxygen blowing decarburization process is adopted without precise control of the oxygen blowing amount and the oxygen activity at the end of decarburization, the oxygen activity of the molten steel at the end of RH decarburization will be too high. The molten steel is in an overoxidized state most of the time during the entire steelmaking process, and the difficulty of controlling the oxidizability of the ladle top slag increases. A large amount of Al2O3 inclusions will also be produced in the molten steel during deoxidation, and the cleanliness of the molten steel is difficult to ensure. At the same time, excessive oxygen blowing amount will result in too long oxygen blowing time, and improper selection of the timing to start oxygen blowing and control of the vacuum pressure during oxygen blowing will make it difficult to quickly reduce the vacuum degree, which also restricts the improvement of decarburization efficiency.

[0004] CN112342333A discloses a method for producing ultra-low carbon steel with high efficiency and low oxygen content. By controlling the composition of molten iron, converter smelting process and endpoint, a forced decarburization process and a corresponding gas flow rate system are used in RH refining to reduce the blowing loss and deoxidizer consumption in the blowing process, simplify the RH operation and greatly improve the cleanliness of molten steel. However, the entire RH decarburization process uses the same large gas flow rate, which will inevitably make the carbon-oxygen reaction in the decarburization process too intense, causing serious splashing of molten steel and carbonization of molten steel; and the large argon blowing flow in the early stage of the decarburization reaction will slow down the vacuum pressure drop rate, which will also affect the decarburization efficiency.

[0005] CN116790837A discloses a method for controlling the oxygen activity of molten steel at the end of low decarburization of IF steel. According to the conditions of molten steel, three decarburization modes are developed to reduce the oxygen activity at the end of decarburization, and combined with the insertion depth of the RH immersion tube, the circulation gas flow rate, and the vacuum control, the active oxygen at the end of decarburization of IF steel is reduced while meeting the requirements of efficient decarburization, reducing the consumption of deoxidizer, greatly improving the cleanliness of molten steel and reducing production costs. However, in the RH decarburization process, the influence of oxygen blowing flow rate and oxygen blowing gun position on oxygen utilization rate, steel liquid splashing and decarburization efficiency is not considered; and different steel supply conditions will also affect oxygen utilization rate, and the patent sets the oxygen utilization rate as a fixed value, which will inevitably cause inaccurate calculation of oxygen blowing amount, thereby affecting the precise control of terminal oxygen activity.

[0006] CN115522016A discloses a method for oxygen decarburization in a refining RH furnace. In the oxygen decarburization process, a variable gun position and variable flow rate decarburization process is adopted to solve the problems of low oxygen utilization rate and insufficient molten steel temperature in the oxygen decarburization of the RH furnace. The oxygen consumption, chemical heating fuel and oxygen consumption of oxygen decarburization are greatly reduced, and the decarburization efficiency is significantly improved. However, the oxygen flow rate and oxygen gun position change with time, and it is impossible to effectively determine whether the initial oxygen gun height and oxygen flow rate are suitable for any steel supply conditions; the dynamic flow rate and gun position that change with time will inevitably affect the stable control of the vacuum degree in the oxygen decarburization process, affect the decarburization efficiency, and increase the difficulty of on-site operation in actual production, which is not conducive to rapid on-site implementation. Summary of the invention

[0007] In order to overcome the defects of the above-mentioned prior art, the purpose of the present application is to provide a method for RH refining oxygen blowing decarburization, improve oxygen utilization, shorten the decarburization cycle, solve the problem of carbon increase in molten steel caused by splashing of molten steel due to excessive carbon-oxygen reaction, achieve RH efficient decarburization, and also help to reduce the oxidizability of the ladle top slag and improve the cleanliness of the molten steel.

[0008] To achieve the above objectives, this application provides the following technical solutions:

[0009] A method for RH refining oxygen blowing decarburization, comprising:

[0010] Dynamically adjust the oxygen blowing flow rate and oxygen blowing gun position according to the carbon and oxygen content ratio of the incoming steel at RH;

[0011] The oxygen blowing amount is determined according to the initial carbon and oxygen contents in the steel entering the RH station and the target carbon and oxygen contents in the molten steel at the end of decarburization;

[0012] A gradient gas flow rate system is adopted in the RH decarburization process.

[0013] Optional, dynamically adjust oxygen flow and oxygen lance position according to the carbon and oxygen content ratio of the incoming RH steel, including:

[0014] When RH enters the steel, W C / W O <0.5, no oxygen decarburization is performed;

[0015] When RH enters the steel, 0.5≤W C / W O <1.0, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing gun position is H=(H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is taken as 1;

[0016] When RH enters the steel, 1.0≤W C / W O <1.5, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing flow adjustment coefficient β is taken as 2, and the oxygen blowing gun position is taken as H = (H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is taken as 2;

[0017] When RH enters the steel, 1.5≤W C / W O <2.0, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing flow adjustment coefficient β is taken as 1; the oxygen blowing gun position is taken as H = (H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is 3;

[0018] When RH enters the steel station, W C / W O ≥2.0, the oxygen flow rate used for RH oxygen decarburization is The oxygen lance position is H=H max , in the later stage of RH refining oxygen blowing process, lower the gun position and increase the oxygen blowing flow rate;

[0019] Among them, W C W is the mass percentage of carbon in the RH incoming steel, O is the mass percentage of oxygen in the RH incoming steel, The upper limit of oxygen blowing flow rate used in RH refining, is the lower limit of oxygen blowing flow rate used in RH refining, H max The upper limit of oxygen lance position used in RH refining, H min This is the lower limit of the oxygen lance position used in RH refining.

[0020] Optional, The value is 2500Nm 3 / h, The value is 1000Nm 3 / h,H max The value is 6.0m, H min The value is 4.0m.

[0021] Optionally, the oxygen blowing amount is determined according to the initial values ​​of carbon and oxygen content in the incoming RH steel and the target values ​​of carbon and oxygen content in the molten steel at the end of decarburization. The calculation formula is as follows:

[0022]

[0023] Where: is the required oxygen blowing amount, m 3 ; W is the total weight of the RH incoming steel, kg; w[C]0 and w[O]0 are the initial carbon and oxygen content of the RH incoming steel, %; w[C] aim , w[O] aim are the target mass percentages of carbon and oxygen content in the molten steel at the end of decarburization, %; η is the average oxygen utilization rate, ranging from 40% to 80%.

[0024] Optionally, the calculation formula for the time consumed in the RH refining oxygen blowing process is as follows:

[0025]

[0026] Where, t start is the time to start blowing oxygen, s; t end The oxygen blowing end time, s; is the oxygen blowing flow rate, Nm 3 / h; is the required oxygen blowing amount, m 3 .

[0027] Optionally, a gradient gas flow rate regime is used during the RH decarburization process, including:

[0028] From the start of vacuuming to oxygen blowing, the lifting gas flow rate is maintained at 120-140m 3 / h;

[0029] During the oxygen blowing process, the lifting gas flow rate is maintained at 150-170m 3 / h;

[0030] From the end of oxygen blowing to the end of decarburization, the lifting gas flow rate is maintained at 190-210m 3 / h.

[0031] Optionally, oxygen blowing is started 100-120 seconds after the start of vacuuming.

[0032] Optionally, the vacuum pressure during oxygen blowing is kept below 100 mbar.

[0033] Optionally, the oxygen content in the molten steel is controlled to be 150-250 ppm at the end of decarburization.

[0034] Technical effects and advantages of this application:

[0035] 1. Compared with the traditional decarburization process using fixed oxygen blowing flow rate and oxygen blowing gun position, the present application dynamically adjusts the oxygen blowing flow rate and oxygen blowing gun position according to the different RH inlet molten steel composition and adopts a gradient gas flow rate system, which can effectively improve the oxygen utilization rate, shorten the decarburization cycle, solve the problem of steel liquid carbonization caused by steel liquid splashing due to excessive carbon-oxygen reaction, and achieve RH efficient decarburization;

[0036] 2. The present application controls the oxygen content of liquid steel to be in the range of 150-250ppm at the end of RH decarburization, and performs oxygen blowing 100-120s after the start of vacuuming, and the vacuum pressure during the oxygen blowing process is maintained below 100mbar, which can reduce the oxygen consumption of RH oxygen blowing decarburization and shorten the oxygen blowing time, while accelerating the pressure drop rate, further improving the decarburization efficiency;

[0037] 3. The method of the present application can perform vacuum oxygen blowing decarburization treatment under the condition that the RH incoming steel liquid has a higher carbon content and a lower oxygen content, thereby achieving high-carbon and low-oxygen steelmaking in the converter and maintaining low oxygen activity of the molten steel during the RH refining process, which is beneficial to reducing the amount of oxygen transferred from the steel to the slag during the ultra-low carbon steel smelting process, reducing the amount of top slag modifier added, and reducing the oxidizability of the top slag. At the same time, the amount of deoxidizer added is reduced, and the amount of Al2O3 inclusions generated in the steel is reduced. The cleanliness of the molten steel is significantly improved, and the production cost is reduced.

[0038] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures indicated in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flow chart of a method for RH refining oxygen decarburization. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0041] like Figure 1 As shown, the present application provides a method for RH refining oxygen blowing decarburization, which is as follows:

[0042] 1. Dynamically adjust the oxygen blowing flow rate and oxygen blowing gun position according to the carbon and oxygen content ratio of the RH incoming steel.

[0043] When RH enters the steel, W C / W O <0.5, no oxygen decarburization is performed;

[0044] When RH enters the steel, 0.5≤W C / W O <1.0, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing gun position is H=(H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is taken as 1;

[0045] When RH enters the steel, 1.0≤W C / W O <1.5, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing flow adjustment coefficient β is taken as 2, and the oxygen blowing gun position is taken as H = (H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is taken as 2;

[0046] When RH enters the steel, 1.5≤W C / W O <2.0, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing flow adjustment coefficient β is taken as 1; the oxygen blowing gun position is taken as H = (H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is 3;

[0047] When RH enters the steel station, W C / W O ≥2.0, the oxygen flow rate used for RH oxygen decarburization is The oxygen lance position is H=H max In order to avoid too long oxygen blowing time, in the later stage of RH refining oxygen blowing process, the gun position can be appropriately lowered and the oxygen blowing flow rate can be increased to accelerate the decarburization efficiency;

[0048] Among them, W C W is the mass percentage of carbon in the RH incoming steel, O is the mass percentage of oxygen in the RH incoming steel, The upper limit of oxygen blowing flow rate used in RH refining is 2500Nm 3 / h, The lower limit of oxygen blowing flow rate used in RH refining is 1000Nm 3 / h,H max The upper limit of the oxygen lance position used in RH refining is 6.0m. min The lower limit of the oxygen lance position used in RH refining is 4.0m.

[0049] 2. Determine the oxygen blowing amount based on the initial values ​​of carbon and oxygen content in the RH incoming steel and the target values ​​of carbon and oxygen content in the molten steel at the end of decarburization.

[0050] The calculation formula for the oxygen blowing amount is as follows:

[0051]

[0052] Where: is the required oxygen blowing amount, m 3 ; W is the total weight of the RH incoming steel, kg; w[C]0 and w[O]0 are the initial carbon and oxygen content of the RH incoming steel, %; w[C] aim , w[O] aim are the target mass percentages of carbon and oxygen content in the molten steel at the end of decarburization, %; η is the average oxygen utilization rate, ranging from 40% to 80%, and the specific value can be determined according to the RH equipment and process conditions.

[0053] Furthermore, the calculation formula for the time consumed in the RH refining oxygen blowing process is as follows:

[0054]

[0055] Where, t start is the time to start blowing oxygen, s; t end The oxygen blowing end time, s; is the oxygen blowing flow rate, Nm 3 / h; is the required oxygen blowing amount, m 3 .

[0056] 3. A gradient gas flow rate system is adopted in the RH decarburization process.

[0057] Start blowing oxygen 100-120s after vacuuming begins. Keep the gas flow rate at 120-140m3 from the start of vacuuming to the start of oxygen blowing. 3 / h;

[0058] During the oxygen blowing process, the lifting gas flow rate is maintained at 150-170m 3 / h, the vacuum pressure during oxygen blowing is kept below 100mbar;

[0059] From the end of oxygen blowing to the end of decarburization, the lifting gas flow rate is maintained at 190-210m 3 / h, in order to minimize the amount of oxygen blown for RH oxygen blowing decarburization, shorten the oxygen blowing time, and maintain a low oxygen activity at the end of decarburization to reduce the amount of aluminum used for deoxidation alloying and improve the cleanliness of the molten steel, the oxygen content in the molten steel is controlled at 150-250ppm at the end of decarburization.

[0060] In order to better illustrate the present invention, the following examples are provided.

[0061] Example 1

[0062] S1: Taking the 200-ton RH unit as an example, the RH incoming steel contains W C =w[C]0=0.043%, W O =w[O]0=0.030%, W C / W O The value is 1.43, and the oxygen blowing flow rate is determined to be 2000Nm 3 / h, oxygen blowing gun position is 5.0m.

[0063] S2: End w[C] with RH decarburization aim =0.0015%, w[O] aim =0.020% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 105Nm 3 .

[0064] S3: The start time of oxygen blowing is 2 minutes, the total consumption time of oxygen blowing is 189 seconds, the end time of oxygen blowing is 5 minutes and 9 seconds, and the vacuum pressure during oxygen blowing decarburization process is maintained between 50-80 mbar.

[0065] S4: From the start of vacuum treatment to 2 minutes after vacuuming, the lifting gas flow rate is maintained at 130m 3 / h; 2min to 5min 9s after vacuuming, the lifting gas flow rate is maintained at 160m 3 / h; 5min 9s to the end of decarburization, the lifting gas flow rate is maintained at 200m 3 / h.

[0066] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0014%, and the mass content of oxygen was 0.021%; the RH decarburization time was 12.5min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.27min -1 , the decarburization rate is significantly improved; the theoretical oxygen utilization rate is calculated to be 62%, and the process significantly improves the oxygen utilization rate; the splashing phenomenon of the molten steel in the vacuum chamber is not strong, and the carbon content of the molten steel is measured to be 0.0016% at the end of RH refining. The carbon increase of the molten steel is only 2ppm, and the carbon increase phenomenon is not obvious.

[0067] The T.Fe of the top slag when entering the RH station is 3.5%, and the T.Fe of the top slag when ending the RH station is 5.5%. The oxidation property of the top slag has not increased significantly. The TO content of the molten steel is 13ppm when ending the RH station, and the molten steel has reached a relatively high purity.

[0068] Example 2

[0069] S1: Taking the 300-ton RH unit as an example, the RH incoming steel contains W C =w[C]0=0.048%, W O =w[O]0=0.028%, W C / W O The value is 1.71, and the oxygen blowing flow rate is determined to be 1500Nm 3 / h, the oxygen blowing gun position is 5.5m.

[0070] S2: End w[C] with RH decarburization aim =0.0012%, w[O] aim =0.022% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 182Nm 3 .

[0071] S3: The start time of oxygen blowing is 1 min 40 s, the total oxygen blowing consumption time is 437 s, the oxygen blowing end time is 7 min 57 s, and the vacuum pressure during the oxygen blowing decarburization process is maintained between 40-60 mbar.

[0072] S4: From the start of vacuum treatment to 1 minute 40 seconds after vacuuming, the lifting gas flow rate is maintained at 140m 3 / h; 1min 40s to 7min 57s after vacuuming, the lifting gas flow rate is maintained at 170m 3 / h; 7min 57s to the end of decarburization, the lifting gas flow rate is maintained at 210m 3 / h.

[0073] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0010%, and the mass content of oxygen was 0.023%; the RH decarburization time was 13.5min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.29min -1 , the decarburization rate is significantly improved; the theoretical oxygen utilization rate is calculated to be 67%, and the process significantly improves the oxygen utilization rate; the splashing phenomenon of the molten steel in the vacuum chamber is not strong, and the carbon content of the molten steel is measured to be 0.0013% at the end of RH refining. The carbon increase of the molten steel is only 3ppm, and the carbon increase phenomenon is not obvious.

[0074] The T.Fe of the top slag entering the RH station is 2.8%, and the T.Fe of the top slag at the end of RH is 4.3%. The oxidation increase of the top slag is not obvious; the TO content of the molten steel is measured to be 15ppm at the end of RH, and the molten steel reaches a relatively high purity.

[0075] Example 3

[0076] S1: Taking the 300-ton RH unit as an example, the RH incoming steel contains W C =w[C]0=0.030%, W O =w[O]0=0.032%, W C / W O The value is 0.88, and the oxygen blowing flow rate is determined to be 2500Nm 3 / h, the oxygen blowing gun position is 4.5m.

[0077] S2: End w[C] with RH decarburization aim =0.0010%, w[O] aim =0.018% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 80Nm 3 .

[0078] S3: The start time of oxygen blowing is 1min 50s, the total oxygen blowing consumption time is 115s, the end time of oxygen blowing is 3min 45s, and the vacuum pressure during the oxygen blowing decarburization process is maintained between 30-50mbar.

[0079] S4: From the start of vacuum treatment to 1 minute 50 seconds after vacuuming, the lifting gas flow rate is maintained at 135m 3 / h; 1min 50s to 3min 45s after vacuuming, the lifting gas flow rate is maintained at 165m 3 / h; 3min 45s to the end of decarburization, the lifting gas flow rate is maintained at 210m 3 / h.

[0080] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0011%, and the mass content of oxygen was 0.019%; the RH decarburization time was 11.0min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.30min -1 , the decarburization rate is significantly improved; the theoretical oxygen utilization rate is calculated to be 67%, and the process significantly improves the oxygen utilization rate; the splashing phenomenon of the molten steel in the vacuum chamber is not strong, and the carbon content of the molten steel is measured to be 0.0014% at the end of RH refining. The carbon increase of the molten steel is only 3ppm, and the carbon increase phenomenon is not obvious.

[0081] The T.Fe of the top slag when entering the RH station is 3.8%, and the T.Fe of the top slag when ending the RH station is 4.7%. The oxidation property of the top slag has not increased significantly. The TO content of the molten steel is 16ppm when ending the RH station, and the molten steel has reached a relatively high purity.

[0082] Example 4

[0083] S1: Taking the 200-ton RH unit as an example, the RH incoming steel contains WC =w[C]0=0.044%, W O =w[O]0=0.020%, W C / W O The value is 2.2, and the oxygen blowing flow rate is determined to be 1000Nm 3 / h, oxygen blowing gun position is 6m, oxygen blowing flow rate increases to 1500Nm in the second half of oxygen blowing 3 / h, and the oxygen lance position is lowered to 5.5m.

[0084] S2: End w[C] with RH decarburization aim =0.0015%, w[O] aim =0.019% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 111Nm 3 .

[0085] S3: The start time of oxygen blowing is 1min 55s, the total oxygen blowing consumption time is 330s, the oxygen blowing end time is 7min 25s, and the vacuum pressure during the oxygen blowing decarburization process is maintained between 20-50mbar.

[0086] S4: From the start of vacuum treatment to 1 minute 55 seconds after vacuuming, the lifting gas flow rate is maintained at 125m 3 / h; 1min 55s to 7min 25s after vacuuming, the lifting gas flow rate is maintained at 160m 3 / h; 7min 57s to the end of decarburization, the lifting gas flow rate is maintained at 195m 3 / h.

[0087] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0014%, and the mass content of oxygen was 0.020%; the RH decarburization time was 12.5min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.28min -1 , the decarburization rate is significantly improved; the theoretical oxygen utilization rate is calculated to be 71%, and the process significantly improves the oxygen utilization rate; the splashing phenomenon of the molten steel in the vacuum chamber is not strong, and the carbon content of the molten steel is measured to be 0.0016% at the end of RH refining. The carbon increase of the molten steel is only 2ppm, and the carbon increase phenomenon is not obvious.

[0088] The T.Fe of the top slag entering the RH station is 4.8%, and the T.Fe of the top slag at the end of RH is 6.3%. The oxidation increase of the top slag is not obvious; the TO content of the molten steel is measured to be 18ppm at the end of RH, and the molten steel reaches a relatively high purity.

[0089] Comparative Example 1

[0090] S1: Taking the 150-ton RH unit as an example, the RH incoming steel contains W C =w[C]0=0.033%, W O=w[O]0=0.035%, W C / W O The value is 0.94, and the oxygen blowing flow rate is determined to be 1800Nm 3 / h, oxygen blowing gun position is 4.0m.

[0091] S2: End w[C] with RH decarburization aim =0.0015%, w[O] aim =0.028% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 74Nm 3 .

[0092] S3: The start time of oxygen blowing is 2 min 40 s, the total oxygen blowing consumption time is 148 s, the end time of oxygen blowing is 5 min 8 s, and the vacuum pressure during the oxygen blowing decarburization process is maintained between 120-140 mbar.

[0093] S4: From the start of vacuum treatment to 2 minutes and 40 seconds after vacuuming, the lifting gas flow rate is maintained at 180m 3 / h; 2min 40s to 5min 8s after vacuuming, the gas flow rate is maintained at 200m 3 / h; 5min 8s until the end of decarburization, the lifting gas flow rate is maintained at 230m 3 / h.

[0094] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0018%, and the mass content of oxygen was 0.026%; the RH decarburization time was 17.5min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.17min -1 , the decarburization rate is significantly reduced, and the decarburization time is significantly extended; the theoretical oxygen utilization rate is calculated to be 46%, and the oxygen utilization rate is significantly reduced; the molten steel splashes strongly in the vacuum chamber, and the carbon content of the molten steel is measured to be 0.0025% at the end of RH refining. The molten steel is carbonized by 7ppm, and the carbon increase phenomenon is obvious.

[0095] The T.Fe of the top slag entering the RH station is 3.1%, and the T.Fe of the top slag at the end of RH is 7.3%. The oxidizability of the top slag has increased significantly; the TO content of the molten steel measured at the end of RH is 25ppm, and the molten steel has not reached a high purity.

[0096] Comparative Example 2

[0097] S1: Taking the 200-ton RH unit as an example, the RH incoming steel contains W C =w[C]0=0.043%, W O =w[O]0=0.032%, W C / W O The value is 1.34, and the oxygen blowing flow rate is determined to be 2500Nm 3 / h, the oxygen blowing gun position is 4.5m.

[0098] S2: End w[C] with RH decarburization aim =0.0013%, w[O] aim =0.030% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 150Nm 3 .

[0099] S3: The start time of oxygen blowing is 2 min 30 s, the total oxygen blowing consumption time is 216 s, the end time of oxygen blowing is 6 min 6 s, and the vacuum pressure during the oxygen blowing decarburization process is maintained between 130-150 mbar.

[0100] S4: From the start of vacuum treatment to 2 minutes and 30 seconds after vacuuming, the lifting gas flow rate is maintained at 200m 3 / h; 2min 30s to 6min 6s after vacuuming, the gas flow rate is maintained at 200m 3 / h; 6min 6s until the end of decarburization, the lifting gas flow rate is maintained at 200m 3 / h.

[0101] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0014%, and the mass content of oxygen was 0.029%; the RH decarburization time was 18.5min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.19min -1 , the decarburization rate is significantly reduced, and the decarburization time is significantly extended; the theoretical oxygen utilization rate is calculated to be 49%, and the oxygen utilization rate is significantly reduced; the molten steel splashes strongly in the vacuum chamber, and the carbon content of the molten steel is measured to be 0.0024% at the end of RH refining. The molten steel is carbonized by 10ppm, and the carbon increase phenomenon is obvious.

[0102] The T.Fe of the top slag entering the RH station is 4.2%, and the T.Fe of the top slag at the end of RH is 7.5%. The oxidizability of the top slag has increased significantly; the TO content of the molten steel measured at the end of RH is 30ppm, and the molten steel has not reached a high purity.

[0103] Comparative Example 3

[0104] S1: Taking the 300-ton RH unit as an example, the RH incoming steel contains W C =w[C]0=0.040%, W O =w[O]0=0.025%, W C / W O The value is 1.6, and the oxygen blowing flow rate is determined to be 2000Nm 3 / h, oxygen blowing gun position is 5.0m.

[0105] S2: End w[C] with RH decarburization aim =0.0014%, w[O]aim =0.026% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 220Nm 3 .

[0106] S3: The start time of oxygen blowing is 2 min 50 s, the total oxygen blowing consumption time is 396 s, the end time of oxygen blowing is 9 min 26 s, and the vacuum pressure during the oxygen blowing decarburization process is maintained between 110-130 mbar.

[0107] S4: From the start of vacuum treatment to 2 minutes and 50 seconds after vacuuming, the lifting gas flow rate is maintained at 200m 3 / h; 2min 50s to 9min 26s after vacuuming, the lifting gas flow rate is maintained at 210m 3 / h; 9min 26s to the end of decarburization, the lifting gas flow rate is maintained at 220m 3 / h.

[0108] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0015%, and the mass content of oxygen was 0.026%; the RH decarburization time was 18.0min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.18min -1 , the decarburization rate is significantly reduced, and the decarburization time is significantly extended; the theoretical oxygen utilization rate is calculated to be 50%, and the oxygen utilization rate is significantly reduced; the molten steel splashes strongly in the vacuum chamber, and the carbon content of the molten steel is measured to be 0.0023% at the end of RH refining. The molten steel is carbonized by 8ppm, and the carbon increase phenomenon is obvious.

[0109] The T.Fe of the top slag entering the RH station is 4.5%, and the T.Fe of the top slag at the end of RH is 8.3%. The oxidizability of the top slag has increased significantly; the TO content of the molten steel measured at the end of RH is 35ppm, and the molten steel has not reached a high purity.

[0110] Comparative Example 4

[0111] S1: Taking the 200-ton RH unit as an example, the RH incoming steel contains W C =w[C]0=0.031%, W O =w[O]0=0.033%, W C / W O The value is 0.94, and the oxygen blowing flow rate is determined to be 1500Nm 3 / h, oxygen blowing gun position is 6.0m.

[0112] S2: End w[C] with RH decarburization aim =0.0015%, w[O] aim =0.029% is the target carbon oxygen content, and the oxygen blowing amount is determined to be 110Nm 3 .

[0113] S3: The oxygen blowing start time is 3 minutes, the total oxygen blowing consumption time is 264 seconds, the oxygen blowing end time is 7 minutes and 24 seconds, and the vacuum pressure during the oxygen blowing decarburization process is maintained between 120-140 mbar.

[0114] S4: From the start of vacuum treatment to 3 minutes after vacuuming, the lifting gas flow rate is maintained at 190m 3 / h; 3min to 7min after vacuuming, 24s, the lifting gas flow rate is maintained at 200m 3 / h; 7min 24s to the end of decarburization, the lifting gas flow rate is maintained at 210m 3 / h.

[0115] After testing, at the end point of RH decarburization, the mass content of carbon in the molten steel was 0.0015%, and the mass content of oxygen was 0.028%; the RH decarburization time was 20.0min; after calculation, the overall apparent decarburization rate of RH decarburization was 0.15min -1 , the decarburization rate was significantly reduced, and the decarburization time was significantly extended; the theoretical oxygen utilization rate was calculated to be 44%, and the oxygen utilization rate was significantly reduced; the molten steel splashed violently in the vacuum chamber, and the carbon content of the molten steel was measured to be 0.0024% at the end of RH refining, and the carbon increase of the molten steel was 9ppm, with obvious carbon increase.

[0116] The T.Fe of the top slag entering the RH station is 5.2%, and the T.Fe of the top slag at the end of RH is 8.5%. The oxidizability of the top slag has increased significantly; the TO content of the molten steel is measured to be 33ppm at the end of RH, and the molten steel has not reached a high purity.

[0117] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for RH refining oxygen blowing decarburization, characterized in that: include: Dynamically adjust the oxygen blowing flow rate and oxygen blowing gun position according to the carbon and oxygen content ratio of the incoming steel at RH; The oxygen blowing amount is determined according to the initial carbon and oxygen contents in the steel entering the RH station and the target carbon and oxygen contents in the molten steel at the end of decarburization; A gradient gas flow rate system is adopted in the RH decarburization process.

2. The method of RH refining oxygen blowing decarburization according to claim 1, characterized in that: The oxygen blowing flow rate and oxygen blowing gun position dynamically adjusted according to the carbon and oxygen content ratio in the RH incoming steel include: When RH enters the steel, W C / W O <0.5, no oxygen decarburization is performed; When RH enters the steel, 0.5≤W C / W O <1.0, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing gun position is H=(H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is taken as 1; When RH enters the steel, 1.0≤W C / W O <1.5, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing flow adjustment coefficient β is taken as 2, and the oxygen blowing gun position is taken as H = (H max -H min ) / 4·α+H min , where the oxygen lance position adjustment coefficient α is taken as 2; When RH enters the steel, 1.5≤W C / W O <2.0, the oxygen flow rate used in RH oxygen decarburization is The oxygen blowing flow adjustment coefficient β is taken as 1; the oxygen blowing gun position is taken as H = (H max -H min ) / 4·α+H min , where the oxygen blowing gun position adjustment coefficient α is taken as 3; When RH enters the steel station, W C / W O ≥2.0, the oxygen flow rate used for RH oxygen decarburization is The oxygen lance position is H=H max , in the later stage of RH refining oxygen blowing process, lower the gun position and increase the oxygen blowing flow rate; Among them, W C is the mass percentage of carbon in the RH incoming steel, W O is the mass percentage of oxygen in the RH incoming steel, The upper limit of oxygen blowing flow rate used in RH refining, is the lower limit of oxygen blowing flow rate used in RH refining, H max The upper limit of oxygen lance position used in RH refining, H min This is the lower limit of the oxygen lance position used in RH refining.

3. The method of RH refining oxygen blowing decarburization according to claim 2, characterized in that: The value is 2500Nm 3 / h, The value is 1000Nm 3 / h,H max The value is 6.0m, H min The value is 4.0m.

4. The method for RH refining oxygen blowing decarburization according to claim 1, characterized in that: The oxygen blowing amount is determined according to the initial values ​​of carbon and oxygen content in the RH incoming steel and the target values ​​of carbon and oxygen content in the molten steel at the end of decarburization. The calculation formula is as follows: Where: is the required oxygen blowing amount, m 3 ; W is the total weight of molten steel entering the RH station, kg; w[C]0 and w[O]0 are the initial carbon and oxygen contents of the steel entering the RH station, % by mass; w[C] aim , w[O] aim are the target mass percentages of carbon and oxygen content in the molten steel at the end of decarburization, %; η is the average oxygen utilization rate, ranging from 40% to 80%.

5. The method of RH refining oxygen blowing decarburization according to claim 4, characterized in that: The calculation formula for the time consumed in the RH refining oxygen blowing process is as follows: Where, t start is the oxygen blowing start time, s; t end The oxygen blowing end time, s; is the oxygen blowing flow rate, Nm 3 / h; V O2 is the required oxygen blowing amount, m 3 .

6. The method of RH refining oxygen blowing decarburization according to claim 1, characterized in that: The gas flow rate gradient system used in the RH decarburization process includes: From the start of vacuuming to oxygen blowing, the lifting gas flow rate is maintained at 120-140m 3 / h; During the oxygen blowing process, the lifting gas flow rate is maintained at 150-170m 3 / h; From the end of oxygen blowing to the end of decarburization, the lifting gas flow rate is maintained at 190-210m 3 / h.

7. The method of RH refining oxygen blowing decarburization according to claim 6, characterized in that: Start blowing oxygen 100-120 seconds after the start of vacuuming.

8. The method of RH refining oxygen blowing decarburization according to claim 6, characterized in that: The vacuum pressure during oxygen blowing is kept below 100 mbar.

9. The method of RH refining oxygen blowing decarburization according to claim 6, characterized in that: At the end of decarburization, the oxygen content in the molten steel is controlled at 150-250ppm.

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