A top slag modification process for ultra-low carbon steel

Abstract

The invention discloses a top slag modification process for ultra-low carbon steel, and belongs to the field of converter and refining technology. In the modification process of the invention, when the converter is tapping steel, carbon powder, lime, medium carbon ferromanganese and aluminum particles are added to perform the first step of modification, and a certain oxidizability of the top slag is retained; during the RH decarburization process, the top slag is used to transfer oxygen to the molten steel to achieve the second step of modification; and after the RH treatment is completed and the air is broken, aluminum particles are added to perform the third step of modification. The invention performs the modification in stages and reasonably controls the oxidizability of the ladle top slag, so that the oxidizability of the top slag is utilized as a resource. In the control process of the whole process, a large amount of instantaneous smoke and dust will not be generated, which is environmentally friendly and the modification is accurate. After the RH air is broken, the T.Fe of the top slag is ≤8%, and the CaO / Al2O3 is in the range of 1.3-1.8. Compared with the traditional top slag modification process, low-cost, low-pollution and more accurate top slag modification is achieved.

Description

Technical Field

[0001] The invention belongs to the field of converter and refining technology, and more specifically, relates to a top slag modification process for ultra-low carbon steel. Background Art

[0002] During the converter tapping process, the highly oxidizing slag in the converter will inevitably be brought into the ladle by the molten steel. There is an iron-oxygen balance and a carbon-oxygen balance at the converter end and during the tapping process. In the IF steel production process, due to the low carbon at the converter end, the molten steel is directly in contact with the air during the tapping process, which may lead to an increase in the oxygen content in the molten steel, and then an increase in the oxidation of the top slag. For IF steel production, during the RH decarburization process, as the oxygen content of the molten steel decreases, the top slag will transfer oxygen to the molten steel. The decarburization process will naturally consume the oxygen in the top slag, reducing the oxidation of the top slag. If a large amount of reducing modifiers are added during the tapping process, the oxidation of the top slag will be extremely low and the oxygen content of the molten steel will decrease. The RH treatment process requires forced oxygen blowing for decarburization. At this time, the oxygen in the molten steel will be transferred to the top slag, resulting in an increase in the oxidation of the top slag. Therefore, reasonable control of the oxygen content in the molten steel during the tapping process can effectively control the oxidation of the top slag.

[0003] The harm of top slag to molten steel mainly occurs during the process from the end of refining to continuous casting. The top slag will transfer oxygen to the molten steel, causing secondary oxidation of the molten steel. Because the molten steel in this process does not have good dynamic stirring conditions, the secondary oxidized inclusions are not easy to float up, which directly deteriorates the quality of the ingot.

[0004] After searching, the application case with Chinese patent application number 201210122599.7 discloses a deoxidizing modifier for ladle top slag. The main components of the modifier in this application include by mass percentage: Al: 30-50%, CaO: 50-30%, Al2O3: 5.0-8.0%, SiO2: ≤3.0%, S+P≤0.07%, C: 0.7-1.4%, CaF2: 3.0-8.0%, H2O≤0.2%. The modifier in this application is a reducing modifier, which can solve the oxidation problem of ladle top slag in the production process of low-carbon steel and provide guarantee for vacuum desulfurization and purification production of pipeline steel. However, in this application, the modifier is added to the surface of ladle top slag after the converter is tapped. At this time, the top slag and the modifier react rapidly, rapidly generating a large amount of smoke, polluting the air and seriously affecting the occupational health of employees.

[0005] For example, the Chinese patent application No. 201811398543.8 discloses a smelting method for controlling the oxidizability of the top slag of IF steel. The smelting method of this application includes four major processes: converter smelting LD, LF furnace refining, RH refining and continuous casting CC. At the end of RH refining, the oxidizability of the top slag and the oxygen content in the steel are more stable. However, in this application, the LF furnace is used for refining after the steel is tapped, which adds a refining process to the IF production process, resulting in a long production rhythm, large heat loss, and a significant increase in production costs. Summary of the invention

[0006] 1. Problems to be solved

[0007] In view of at least some of the problems existing in the above prior art, the present invention proposes a top slag modification process for ultra-low carbon steel. The present invention adopts staged modification to make resource utilization of the oxidizing property of the ladle top slag, while also avoiding the generation of a large amount of smoke and dust during the top slag modification process, so as to achieve the purpose of green, environmentally friendly and low-cost modification.

[0008] 2. Technical solution

[0009] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] The ultra-low carbon steel top slag modification process of the present invention comprises the following steps:

[0011] Step 1: After the converter blowing is completed, pre-deoxidized carbon powder, lime, medium carbon ferromanganese and aluminum particles are added for the first reforming, and a certain oxidizability of the top slag is retained.

[0012] (1) After the converter blowing is completed, the molten steel is oxygenated and the converter end point oxygen [O] is measured. 终点 ,, according to the converter end point oxygen [O] 终点 and the carbon oxygen accumulation [C] [O] of the last furnace on the furnace seat, and adding pre-deoxidized carbon powder during the steel tapping process;

[0013] (2) According to the converter end oxygen [O] 终点 Add lime and medium carbon ferromanganese during steel tapping;

[0014] (3) According to the converter end oxygen [O] 终点 After the steel is tapped, aluminum particles are added to the slag surface at the top of the ladle;

[0015] Step 2: During RH decarburization, top slag is used to transfer oxygen to the molten steel to achieve the second step of reforming and control the oxygen concentration at the end of decarburization.

[0016] (1) The ladle is opened to the sampling position behind the furnace, or the argon blowing station behind the furnace, and the sampling operation is carried out. The carbon content of the sample is [C] CT , the unit is ppm;

[0017] (2) After the molten steel enters the RH station, the temperature and oxygen are measured and the oxygen value is [O] RH , according to different [O] RH Calculation of oxygen consumption for decarburization of molten steel[O] 耗氧 , at the same time, RH decarburization ends oxygen [O] 脱碳结束 Adjust to the target value;

[0018] Step 3: After the RH refining treatment is completed, aluminum particles are added again during the air breaking process;

[0019] Step 4: Protect pouring.

[0020] Preferably, in the step 1, all the carbon powder is added before 1 / 2 of the steel is tapped, and the specific amount of carbon powder added is:

[0021] [C][O]≤18, [O] 终点 ≤400, carbon powder addition amount 0.1±0.02kg / t, [O] 终点 >400, carbon powder addition amount 0.15±0.02kg / t;

[0022] 18<[C][O]≤23, [O] 终点 ≤450, carbon powder addition amount 0.12±0.02kg / t, [O] 终点 >450, carbon powder addition amount 0.15±0.02kg / t;

[0023] 23<[C][O], [O] 终点 ≤500, carbon powder addition amount 0.14±0.02kg / t, [O] 终点 >500, carbon powder addition amount 0.17±0.02kg / t.

[0024] Preferably, in the step 1, all the lime is added before 1 / 2 of the steel is tapped, and the specific amount of lime added is:

[0025] [O] 终点 <550, lime addition amount 2±0.2kg / t;

[0026] 550≤[O] 终点 ≤650, lime addition amount 2.4±0.2kg / t;

[0027] [O] 终点 >650, lime addition amount 2.8±0.2kg / t.

[0028] Preferably, in the step 1, the amount of medium carbon ferromanganese added is: 中碳锰铁 =([Mn%] 目标 -0.12)*W 钢水量 *10 / β, where W 中碳锰铁is the amount of medium carbon ferromanganese added, [Mn%] 目标 is the target value of manganese element in steel grade, W 钢水量 is the amount of molten steel, and β is the manganese content of medium carbon ferromanganese alloy.

[0029] Preferably, in the step 1, the timing of adding aluminum particles is that when the steel tapping is completed, aluminum particles are added to the slag surface of the ladle, and at the same time, the ladle car moves toward the converter and then moves in the opposite direction to the steel tapping position.

[0030] Preferably, in step 1, the specific amount of aluminum particles added is: [0] 终点 <550, adding amount 0.13±0.1kg / t;

[0031] 550≤[O] 终点 <650, adding amount 0.15±0.1kg / t;

[0032] 650≤[O] 终点 <750, adding amount 0.17±0.1kg / t;

[0033] 750≤[O] 终点 , added amount 0.19±0.1kg / t.

[0034] Preferably, in the step 2, the oxygen consumption for decarburization of molten steel is [O] 耗氧 =[C] CT ×λ, where λ is the oxygen consumption coefficient, ranging from 0.79 to 0.86.

[0035] Preferably, in step 2, the specific operation of adjusting to the target value is:

[0036] If [O] RH -([O] 耗氧 +[O] 脱碳结束 )>20ppm, add carbon powder to deoxidize to the target value, carbon powder addition amount C 加入量 =W 钢水量 ×([O] RH -([O] 耗氧 +[O] 脱碳结束 )×1.33 / 1000;

[0037] If [O] RH -([O] 耗氧 +[O] 脱碳结束 )<-20ppm, top gun oxygen supply value target value, oxygen blowing amount O 吹氧量 =-(W 钢水量 ×([O] RH -([O] 耗氧 +[O] 脱碳结束 ))×1.429 / 1000.

[0038] Preferably, in the step 3, aluminum particles are added when the vacuum degree is reduced to 300-450 mbar.

[0039] Preferably, in step 3, the specific amount of aluminum particles added is: [0] 脱碳结束 <150, adding amount 0.14±0.01kg / t;

[0040] 150≤[O] 脱碳结束 <200, adding amount 0.16±0.01kg / t;

[0041] 200≤[O] 脱碳结束 <250, adding amount 0.18±0.01kg / t;

[0042] 250≤[O] 脱碳结束 <300, adding amount 0.20±0.01kg / t;

[0043] 300≤[O] 脱碳结束 <350, adding amount 0.22±0.01kg / t;

[0044] 350≤[O] 脱碳结束 <400, adding amount 0.24±0.01kg / t;

[0045] 400≤[O] 脱碳结束 <450, adding amount 0.14±0.01kg / t;

[0046] [O] 脱碳结束 ≥450, added amount 0.28±0.01kg / t.

[0047] 3. Beneficial effects

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The ultra-low carbon steel top slag modification process of the present invention performs the first modification when the converter is tapping steel, retains a certain oxidizability of the top slag, utilizes the top slag to transfer oxygen to the molten steel during RH decarburization to achieve the second modification, and performs the third modification after the RH treatment is completed and the air is broken; the modification process of the present invention makes resourceful use of the oxidizability of the top slag, avoids excessive modification during the steel tapping process, which leads to RH oxygen blowing decarburization, reduces the RH decarburization rate, and increases the RH oxygen blowing decarburization ratio, and also avoids the molten steel transferring oxygen to the top slag during the RH decarburization treatment, which leads to an increase in the oxidizability of the top slag and deteriorates the modification effect of the steel tapping process; at the same time, it also avoids the generation of a large amount of smoke and dust during the top slag modification process, providing technical support for improving the enterprise environment and protecting the occupational health of employees.

[0050] (2) The ultra-low carbon steel top slag modification process of the present invention can generate CO and CO2 gases during the reaction process by adding carbon powder and lime during the steel tapping process, so as to promote deep modification of the top slag and provide certain kinetic conditions for adding aluminum particles after the steel tapping is completed, thereby ensuring that the aluminum particles can be melted smoothly; in addition, the oxidizability in the slag can be reduced, the basicity in the slag can be increased, and rephosphorization can be prevented; medium carbon ferromanganese is added during the steel tapping process for preliminary alloying, which can reduce the amount of subsequent RH alloy added and improve RH production efficiency.

[0051] (3) In the ultra-low carbon steel top slag modification process of the present invention, since carbon powder has a relatively light specific gravity, carbon powder is added first, and then lime and medium carbon ferromanganese are added to effectively prevent the overflow of carbon powder and ensure that the carbon powder can be fully integrated into the molten steel; at the same time, the carbon powder and lime are all added before 1 / 2 of the steel is tapped, so that the dynamic conditions of the molten steel during the tapping process can be utilized to make the integration of carbon powder and lime more uniform.

[0052] (4) In the process of modifying the top slag of ultra-low carbon steel of the present invention, after the steel is tapped, the furnace simultaneously adds aluminum particles to the slag surface of the ladle. At this time, the aluminum particles are quickly melted under the action of the high-temperature molten slag and react with the oxides in the top slag of the ladle. The smoke generated by the reaction is promptly taken away by the converter dust collector. At the same time, during the process of adding aluminum particles, the ladle car moves toward the converter, and after moving about 1 / 3 of the diameter of the ladle, it moves in the opposite direction to the steel tapping position. This operation prevents the aluminum particles from accumulating on the top slag of the ladle and generating smoke for a long time.

[0053] (4) In the ultra-low carbon steel top slag modification process of the present invention, when the vacuum degree is reduced to 300-450mbar after RH refining, aluminum particles are added for the second time. On the one hand, this is to further modify the ladle top slag in depth and reduce the transfer of oxygen in the top slag to the molten steel during the continuous casting process; on the other hand, this is to prevent the excessive modification of the top slag before the RH enters the station, which consumes oxygen in the molten steel and affects the RH decarburization, thereby affecting the quality of the molten steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The present invention is a flow chart of an ultra-low carbon steel top slag modification process. DETAILED DESCRIPTION

[0055] The present invention provides a green and environmentally friendly modification process for ultra-low carbon steel top slag, comprising the following steps:

[0056] (1) After the converter blowing is completed, the molten steel is oxygenated for the first time. 终点And the carbon oxygen accumulation [C][O] of the furnace on the furnace seat, pre-deoxidized carbon powder is added during the steel tapping process. The carbon powder reacts with the oxidizing substances in the slag steel, on the one hand, it will reduce the oxidizing property in the slag; on the other hand, the carbon oxygen reaction will produce CO and CO2 gases to promote the deep modification of the top slag. In addition, all the carbon powder is added before 1 / 2 of the steel is tapped to make full use of the dynamic conditions of the molten steel during the steel tapping process, so that the carbon powder can be integrated more quickly and evenly. Among them, the specific amount of carbon powder added is shown in Table 1.

[0057] Table 1. Carbon powder addition amount during steel tapping

[0058]

[0059] [O] 终点 : converter end point oxygen, ppm;

[0060] [C][O]: Carbon and oxygen accumulation at the end of the converter.

[0061] (2) Lime is added during the steel-making process. On the one hand, lime can dilute the oxidizing property in the slag. Limestone decomposes when heated to produce CO2, which promotes deep modification of the top slag. On the other hand, it can increase the alkalinity in the slag to prevent phosphorus reversion. Similarly, it is preferred that all lime is added before 1 / 2 of the steel is made. The specific amount of lime added is shown in Table 2.

[0062] Table 2 Lime addition amount during steel tapping process

[0063]

[0064] (3) Preliminary alloying is performed during the steelmaking process, and medium carbon ferromanganese is added for preliminary alloying, mainly to reduce the amount of RH alloy added and improve RH production efficiency. 中碳锰铁 =([Mn%] 目标 -0.12)*W 钢水量 *10 / β,

[0065] W 中碳锰铁 : Medium carbon ferromanganese addition amount;

[0066] [Mn%] 目标 : Target value of manganese element for steel grade;

[0067] W 钢水量 : Molten steel volume;

[0068] β: manganese content of medium carbon ferromanganese alloy, calculated based on laboratory analysis data, and taken as 0.8 in the present invention.

[0069] (4) After blowing, according to the oxygen value [O] 终点After the steel is tapped, aluminum particles are added to the slag surface at the top of the ladle. The purpose of adding aluminum particles is to react with the oxidizing substances in the slag to reduce the oxidizing properties of the slag, thereby achieving the purpose of reducing the oxidizing substances in the slag. The specific feeding requirements are shown in Table 3.

[0070] Table 3. Amount of aluminum particles added at the end of blowing

[0071] Converter end point oxygen (ppm) [O]＜550 550≤[O]＜650 650≤[O]＜750 750≤[O] Aluminum granule addition amount kg / t 0.13±0.1 0.15±0.1 0.17±0.1 0.19±0.1

[0072] Timing of adding aluminum particles after steel tapping: When steel tapping is completed, aluminum particles are added to the slag surface of the ladle. Under the action of high-temperature molten slag, the aluminum particles melt quickly and react with the oxides on the top slag of the ladle. The smoke and dust produced by the reaction are taken away by the converter dust collector.

[0073] After the steel is tapped, the ladle car moves: the ladle car moves toward the converter immediately after the steel is tapped. After moving about 1 / 3 of the ladle diameter, it moves in the opposite direction to the tapping position. This operation prevents aluminum particles from accumulating on the top slag of the ladle and generating smoke for a long time. When it is confirmed that there is no white smoke on the top slag of the ladle, the ladle is opened to the hanging position.

[0074] (5) After the ladle is opened to the sampling position behind the furnace or the argon blowing station behind the furnace, sampling operation is carried out. The carbon content of the sample is [C] CT ,

[0075] The unit is ppm. At the same time, the molten steel undergoes a second oxygen determination operation after entering the RH station, and the oxygen determination value is [O] RH , the unit is ppm;

[0076] RH decarburization end oxygen control, through extremely low decarburization end oxygen control, consumes oxygen in the top slag and reduces the oxidizability of the top slag:

[0077] Table 4. Decarburization end oxygen target for different steel grades

[0078]

[0079] [O] 脱碳结束 : RH decarburization end oxygen (ppm).

[0080] Calculate oxygen consumption for decarburization of molten steel according to different oxygen values: [O] 耗氧 =[C] CT ×λ

[0081] [O] 耗氧 : Oxygen consumption for decarburization of molten steel, ppm;

[0082] λ: oxygen consumption coefficient.

[0083] Table 5. Oxygen consumption coefficient corresponding to different converter end oxygen

[0084]

[0085] If [O] RH -([O] 耗氧 +[O] 脱碳结束 )>20ppm, add carbon powder to deoxidize to the target value;

[0086] Carbon powder added amount: C 加入量 =W 钢水量 ×([O] RH -([O] 耗氧 +[O] 脱碳结束 )×1.33 / 1000

[0087] If [O] RH -([O] 耗氧 +[O] 脱碳结束 )<-20ppm, top gun oxygen blowing oxygen supply value target value;

[0088] Oxygen blowing amount: O 吹氧量 =-(W 钢水量 ×([O] RH -([O] 耗氧 +[O] 脱碳结束 ))×1.429 / 1000.

[0089] (6) After RH refining breaks the vacuum and the vacuum degree drops to 300-450 mbar, aluminum is added to the molten slag dripping in the vacuum chamber, so that the high-aluminum molten slag drips onto the surface of the ladle top slag to modify the active top slag of the ladle.

[0090] The specific operation is that 2 minutes before breaking the air, the amount of aluminum particles added is input into the weighing hopper of the silo according to Table 6. The silo is linked to the vacuum degree. When the vacuum degree drops to 300mbar, aluminum particles are added. At this time, aluminum particles are added: on the one hand, the top slag of the ladle is further modified in depth to reduce the transfer of oxygen in the top slag to the molten steel during continuous casting; on the other hand, the top slag is modified to reduce the transition before the RH enters the station, which consumes oxygen in the molten steel and affects the decarburization of RH. In order to decarburize, RH needs to be heated by blowing oxygen, which reduces the quality of the molten steel.

[0091] Table 6, RH aluminum particle addition amount

[0092] Decarburization end oxygen (ppm) [O]＜150 150≤[O]＜200 200≤[O]＜250 250≤[O]＜300 Aluminum particles (kg / t) 0.14±0.01 0.16±0.01 0.18±0.01 0.2±0.01 Decarburization end oxygen (ppm) 300≤[O]＜350 350≤[O]＜400 400≤[O]＜450 [O]≥450 Aluminum particles (kg / t) 0.22±0.01 0.24±0.01 0.26±0.01 0.28±0.01

[0093] The invention discloses a green and environmentally friendly modification process for ultra-low carbon steel top slag. Through staged modification, the modification cost is low while ensuring a suitable calcium-aluminum ratio. At the same time, it also avoids the instantaneous generation of a large amount of smoke and dust during the top slag modification process, providing technical guarantee for the improvement of the enterprise environment and the occupational health of employees. The final oxidation property of the ladle top slag TFe≤8%, and the calcium-aluminum ratio (CaO / Al2O3) is controlled within the range of 1.3-1.8, realizing the purpose of green and environmentally friendly low-cost modification.

[0094] In addition, by rationally controlling the oxidation of the ladle top slag in stages, the oxidation of the top slag is utilized as a resource, avoiding excessive modification during the steel-making process, resulting in RH oxygen decarburization, reducing the RH decarburization rate, and increasing the RH oxygen decarburization ratio. It also avoids the transfer of oxygen from the molten steel to the top slag during the RH decarburization process, resulting in increased oxidation of the top slag, deteriorating the modification effect of the steel-making process, and causing modification failure.

[0095] The present invention is further described below in conjunction with specific embodiments.

[0096] Example 1

[0097] The present embodiment is a green and environmentally friendly modification process of ultra-low carbon steel top slag, taking 300T converter and refining production as an example. Among them, the steel type is DC04, and the DC04 steel RH molten steel composition requirements are specifically shown in Table 7:

[0098] Table 7. Requirements for composition of DC04 steel RH molten steel

[0099] Require C Si Mn P S Als Ti Control requirements ≤0.0050 ≤0.03 0.10～0.30 ≤0.015 ≤0.012 0.020～0.070 0.04-0.08 RH target value 0.0025 ≤0.03 0.20 ≤0.015 ≤0.012 0.045 0.06

[0100] In this embodiment, the amount of molten steel is 311 tons; after the converter blowing is completed, the molten steel is oxygenated, and the [O] end point = 496ppm; the carbon oxygen accumulation of one furnace on the furnace seat is 17.

[0101] According to Table 1, 0.14kg / t of carbon powder is added before 1 / 2 of the steel is tapped, and 44kg of carbon powder is actually added. According to Table 2, 2kg / t of lime is added during the tapping process, and 621kg is actually added. After the tapping is completed, aluminum particles are added to the slag surface on the top of the ladle, and according to Table 3, 0.13kg / t is calculated, and 41kg is actually added.

[0102] During the steel-making process, preliminary alloying is performed by adding medium carbon ferromanganese;

[0103] W 中碳锰铁 =([Mn%] 目标 -0.12)*W 钢水量 *10 / β=(0.20-0.12)*311*10 / 0.8=311kg.

[0104] Sampling and analysis at the argon blowing station [C]CT is 231ppm; after the molten steel enters the RH station, the temperature and oxygen determination operation are carried out, and the oxygen determination value is [O] RH It is 399ppm.

[0105] According to Table 7, the RH exit carbon requirement of this steel grade is 0.0025%. According to Table 4, the RH decarburization end oxygen [O] 脱碳结束 is 140±20; according to Table 5, the oxygen consumption coefficient λ is 0.85; then, [O] RH -([O] 耗氧 +[O] 脱碳结束 )=63ppm>20ppm, carbon powder deoxidation operation is required.

[0106] C 加入量 =W 钢水量 ×([O] RH -([O] 耗氧 +[O] 脱碳结束 )×1.33 / 1000=26.5kg, 26kg is actually added.

[0107] At the end of decarburization, the oxygen content was 132 ppm. When the vacuum degree dropped to 300 mbar after RH refining, according to Table 6, 44 kg of aluminum particles were actually added. After RH refining, the T.Fe of the top slag was 6.5%, and the CaO / Al2O3 was 1.5.

[0108] Example 2

[0109] The present embodiment is a green and environmentally friendly modification process of ultra-low carbon steel top slag, taking 300T converter and refining production as an example. The steel type is DC06, and the DC06 steel RH molten steel composition requirements are shown in Table 8:

[0110] Table 8. Requirements for composition of DC06 steel RH molten steel

[0111] Require C Si Mn P S Als Ti Control requirements ≤0.0025 ≤0.03 0.10～0.25 ≤0.015 ≤0.012 0.020～0.070 0.04-0.08 RH target value 0.0015 ≤0.03 0.16 ≤0.015 ≤0.010 0.05 0.06

[0112] In this embodiment, the amount of molten steel is 308 tons; after the converter blowing is completed, the molten steel is oxygenated, [O] 终点 =456ppm; the carbon oxygen accumulation of one furnace on this furnace seat is 19.

[0113] According to Table 1, 0.15kg / t of carbon powder is added before 1 / 2 of the steel is tapped, and 46kg of carbon powder is actually added. According to Table 2, 2kg / t of lime is added during the tapping process, and 615kg is actually added. After the tapping is completed, aluminum particles are added to the slag surface on the top of the ladle, and according to Table 3, 0.13kg / t is calculated, and 40kg is actually added.

[0114] During the steel-making process, preliminary alloying is performed by adding medium carbon ferromanganese;

[0115] W medium carbon ferromanganese = ([Mn%] 目标 -0.12)*W 钢水量 *10 / β=(0.16-0.12)*308*10 / 0.8=154kg.

[0116] Sampling and analysis at the argon blowing station [C] CT is 341ppm; after the molten steel enters the RH station, the temperature and oxygen determination operation are carried out, and the oxygen determination value is [O] RH It is 402ppm.

[0117] According to Table 8, the RH exit carbon requirement of this steel grade is 0.0015%. According to Table 4, the RH decarburization end oxygen [O] 脱碳结束 is 180±20; according to Table 5, the oxygen consumption coefficient λ is 0.85; then, [O] RH -([O] 耗氧 +[O] 脱碳结束 )=-68ppm<-20ppm, oxygen blowing operation is required.

[0118] C 吹氧量 =-(W 钢水量 ×([O]RH-([O] 耗氧 +[O] 脱碳结束 ))×1.429 / 1000=30m 3 , actual oxygen blowing 30m 3 .

[0119] At the end of decarburization, the oxygen content was 168 ppm. When the vacuum degree dropped to 300 mbar after RH refining, according to Table 6, 49 kg of aluminum particles were actually added. After RH refining, the T.Fe of the top slag was 6.8%, and the CaO / Al2O3 was 1.6.

[0120] Example 3

[0121] The present embodiment is a green and environmentally friendly modification process of ultra-low carbon steel top slag, taking 300T converter and refining production as an example. The steel type is DC06, and the DC06 steel RH molten steel composition requirements are shown in Table 8.

[0122] In this embodiment, the amount of molten steel is 315 tons; after the converter blowing is completed, the molten steel is oxygenated. 终点 =562ppm; the carbon oxygen accumulation of one furnace on this furnace seat is 24.

[0123] According to Table 1, 0.17kg / t of carbon powder is added before 1 / 2 of the steel is tapped, and 54kg of carbon powder is actually added. According to Table 2, 2.4kg / t of lime is added during the tapping process, and 755kg is actually added. After the tapping is completed, aluminum particles are added to the slag surface on the top of the ladle, and according to Table 3, 0.15kg / t is calculated, and 46kg is actually added.

[0124] During the steel-making process, preliminary alloying is performed by adding medium carbon ferromanganese;

[0125] W medium carbon ferromanganese = ([Mn%] 目标 -0.12)*W 钢水量 *10 / β=(0.16-0.12)*315*10 / 0.8=157.5kg.

[0126] Sampling and analysis at the argon blowing station [C] CT is 246ppm; after the molten steel enters the RH station, the temperature and oxygen determination operation are carried out, and the oxygen determination value is [O] RH It is 430ppm.

[0127] According to Table 8, the RH exit carbon requirement of this steel grade is 0.0015%. According to Table 4, the RH decarburization end oxygen [O] 脱碳结束 is 180±20; according to Table 5, the oxygen consumption coefficient λ is 0.84; then, [O] RH -([O] 耗氧 +[O] 脱碳结束 )=-36.44ppm<-20ppm, oxygen blowing operation is required.

[0128] C 吹氧量 =-(W 钢水量 ×([O] RH -([O] 耗氧 +[O] 脱碳结束 ))×1.429 / 1000=16.4m 3 , actual oxygen blowing 18m 3 .

[0129] The oxygen content at the end of decarburization was 284 ppm. When the vacuum degree dropped to 300 mbar after RH refining, according to Table 6, 63 kg of aluminum particles were actually added. After RH refining, the T.Fe of the top slag was 7.3%, and CaO / Al2O3 was 1.4.

[0130] Example 4

[0131] The present embodiment is a green and environmentally friendly modification process of ultra-low carbon steel top slag, taking 300T converter and refining production as an example. The steel type is DC06, and the DC06 steel RH molten steel composition requirements are shown in Table 8.

[0132] In this embodiment, the amount of molten steel is 291 tons; after the converter blowing is completed, the molten steel is oxygenated. 终点 =738ppm; the carbon oxygen accumulation of one furnace on this furnace seat is 23.

[0133] According to Table 1, 0.15kg / t of carbon powder is added before 1 / 2 of the steel is tapped, and 44kg of carbon powder is actually added. According to Table 2, 2.8kg / t of lime is added during the tapping process, and 815kg is actually added. After the tapping is completed, aluminum particles are added to the slag surface on the top of the ladle, and according to Table 3, 0.17kg / t is calculated, and 50kg is actually added.

[0134] During the steel-making process, preliminary alloying is performed by adding medium carbon ferromanganese;

[0135] W medium carbon ferromanganese = ([Mn%] 目标 -0.12)*W 钢水量 *10 / β=(0.16-0.12)*291*10 / 0.8=145.5kg.

[0136] Sampling and analysis at the argon blowing station [C] CT is 229ppm; after the molten steel enters the RH station, the temperature and oxygen determination operation are carried out, and the oxygen determination value is [O] RH It is 536ppm.

[0137] According to Table 8, the RH exit carbon requirement of this steel grade is 0.0015%. According to Table 4, the RH decarburization end oxygen [O] 脱碳结束 is 180±20; according to Table 5, the oxygen consumption coefficient λ is 0.81; then, [O] RH -([O] 耗氧 +[O] 脱碳结束 )=170.5ppm>20ppm, it is necessary to add toner.

[0138] C 加入量 =W 钢水量 ×([O] RH -([O] 耗氧 +[O] 脱碳结束 )×1.33 / 1000=66kg, 68kg is actually added.

[0139] The oxygen content at the end of decarburization was 359 ppm. When the vacuum degree dropped to 300 mbar after RH refining, according to Table 6, 87 kg of aluminum particles were actually added. After RH refining, the T.Fe of the top slag was 6.1%, and CaO / Al2O3 was 1.3.

[0140] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A top slag modification process for ultra-low carbon steel, characterized in that: The following steps are included: Step 1: After the converter blowing is completed, pre-deoxidized carbon powder, lime, medium carbon ferromanganese and aluminum particles are added for the first reforming, and a certain oxidizability of the top slag is retained. (1) After the converter blowing is completed, the molten steel is oxygenated and the converter end oxygen [O] is measured. 终点， , according to the converter end point oxygen [O] 终点 and the carbon oxygen accumulation [C] [O] of the last furnace on the furnace seat, and adding pre-deoxidized carbon powder during the steel tapping process; (2) Based on the converter end point oxygen [O] 终点 Add lime and medium carbon ferromanganese during steel tapping; (3) According to the converter end oxygen [O] 终点 After the steel is tapped, aluminum particles are added to the slag surface at the top of the ladle; Step 2: During RH decarburization, top slag is used to transfer oxygen to the molten steel to achieve the second step of reforming and control the oxygen concentration at the end of decarburization. (1) After the ladle is opened to the sampling position behind the furnace or the argon blowing station behind the furnace, sampling operation is carried out and the carbon content of the sample is analyzed as [C] CT , the unit is ppm; (2) After the molten steel enters the RH station, the temperature and oxygen are measured and the oxygen value is [O] RH , according to different [O] RH Calculation of oxygen consumption for decarburization of molten steel[O] 耗氧 , at the same time, RH decarburization ends oxygen [O] 脱碳结束 Adjust to the target value; Step 3: After the RH refining treatment is completed, aluminum particles are added again during the air breaking process; Step 4: Protect pouring; In the step 2, the oxygen consumption for decarburization of molten steel [O] 耗氧 =[C] CT ×λ, where λ is the oxygen consumption coefficient, ranging from 0.79 to 0.86; the specific operation to adjust to the target value is: If [O] RH - ([O] 耗氧 +[O] 脱碳结束 )>20ppm, add carbon powder to deoxidize to the target value, carbon powder addition amount: C 加入量 =W 钢水量 ×([O] RH - ([O] 耗氧 +[O] 脱碳结束 )×1.33 / 1000; If [O] RH - ([O] 耗氧 +[O] 脱碳结束 )<-20ppm, top gun oxygen blowing oxygen supply value target value, oxygen blowing amount: O 吹氧量 =-(W 钢水量 ×([O] RH - ([O] 耗氧 +[O] 脱碳结束 ))×1.429 / 1000.

2. The ultra-low carbon steel top slag modification process according to claim 1, characterized in that: In the step 1, all the carbon powder is added before 1 / 2 of the steel is tapped, and the specific amount of carbon powder added is: [C][O]≤18, [O] 终点 ≤400, carbon powder addition amount 0.1±0.02kg / t, [O] 终点 >400, carbon powder addition amount 0.15±0.02kg / t; 18<[C][O]≤23, [O] 终点 ≤450, carbon powder addition amount 0.12±0.02kg / t, [O] 终点 >450, carbon powder addition amount 0.15±0.02kg / t; 23<[C][O], [O] 终点 ≤500, carbon powder addition amount 0.14±0.02kg / t, [O] 终点 >500, carbon powder addition amount 0.17±0.02kg / t.

3. The ultra-low carbon steel top slag modification process according to claim 2, characterized in that: In the step 1, all the lime is added before 1 / 2 of the steel is tapped, and the specific amount of lime added is: [O] 终点 <550, lime addition amount 2±0.2kg / t; 550≤[O] 终点 ≤650, lime addition amount 2.4±0.2kg / t; [O] 终点 >650, lime addition amount 2.8±0.2kg / t.

4. The ultra-low carbon steel top slag modification process according to claim 3, characterized in that: In the step 1, the amount of medium carbon ferromanganese added is: 中碳锰铁 =([Mn%] 目标 -0.12)*W 钢水量 *10 / β, where W 中碳锰铁 is the amount of medium carbon ferromanganese added, [Mn%] 目标 is the target value of manganese element in steel grade, W 钢水量 is the amount of molten steel, and β is the manganese content of medium carbon ferromanganese alloy.

5. The ultra-low carbon steel top slag modification process according to claim 4, characterized in that: In the step 1, the timing of adding aluminum particles is that when the steel tapping is completed, aluminum particles are added to the slag surface of the ladle, and at the same time, the ladle car moves toward the converter and then moves in the opposite direction to the steel tapping position.

6. The ultra-low carbon steel top slag modification process according to claim 5, characterized in that: In the step 1, the specific amount of aluminum particles added is: [O] 终点 <550, adding amount 0.13±0.1kg / t; 550≤[O] 终点 <650, adding amount 0.15±0.1kg / t; 650≤[O] 终点 <750, adding amount 0.17±0.1kg / t; 750≤[O] 终点 , added amount 0.19±0.1kg / t.

7. A process for modifying top slag of ultra-low carbon steel according to any one of claims 1 to 6, characterized in that: In the step 3, when the vacuum degree is reduced to 300-450 mbar, aluminum particles are added.

8. The ultra-low carbon steel top slag modification process according to claim 7, characterized in that: In the step 3, the specific amount of aluminum particles added is: 脱碳结束 <150, adding amount 0.14±0.01kg / t; 150≤[O] 脱碳结束 <200, adding amount 0.16±0.01kg / t; 200≤[O] 脱碳结束 <250, adding amount 0.18±0.01kg / t; 250≤[O] 脱碳结束 <300, adding amount 0.20±0.01kg / t; 300≤[O] 脱碳结束 <350, adding amount 0.22±0.01kg / t; 350≤[O] 脱碳结束 <400, adding amount 0.24±0.01kg / t; 400≤[O] 脱碳结束 <450, adding amount 0.14±0.01kg / t; [O] 脱碳结束 ≥450, added amount 0.28±0.01kg / t.

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