A method of deoxidizing and alloying an if steel

Abstract

The application discloses a method for deoxidation and alloying of IF steel, which comprises converter smelting, RH refining and continuous casting. In the converter smelting step, lime is first added into the ladle, and then ferrosilicon is added to pre-deoxidize the molten steel and the ladle slag after tapping. In the RH refining step, when the molten steel is decarburized to the qualified carbon content, ferrosilicon is added to pre-deoxidize. After the ferrosilicon is added, aluminum cutting pellets are added to deoxidize and alloy. After the aluminum cutting pellets are added, alloys are added to alloy. In the continuous casting step, the time interval between the start of continuous casting and the end of the RH emptying is controlled to be less than or equal to 30 min, so as to reduce the secondary oxidation of the molten steel. The two-step pre-deoxidization method using ferrosilicon and the final deoxidization process using aluminum cutting pellets not only reduce the deoxidization cost, but also improve the quality of the molten steel.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting technology, and specifically relates to a method for deoxidizing and alloying IF steel. Background Technology

[0002] IF steel, also known as "interstitial atom-free steel," is produced by reducing the content of interstitial elements N and C to extremely low levels during steelmaking. Then, stabilizing elements Ti and Nb, which have a strong affinity for N and C, are added to combine with N and C, forming nitrogen and carbides that are then fixed. This effectively controls the infinitely soluble interstitial atoms to near zero, resulting in steel with superior deep-drawing properties. IF steel is widely used in the automotive and home appliance industries.

[0003] In the metallurgical industry, the process path for IF steel is generally "converter-RH refining furnace-continuous casting machine". The converter is the primary refining furnace, mainly responsible for decarburization, dephosphorization, and temperature adjustment. It typically needs to reduce [C] from approximately 4.5% to approximately 0.04%, and [P] from approximately 0.10% to approximately 0.012%. To ensure effective decarburization and dephosphorization, a high oxygen content must be maintained before tapping. During the converter tapping process, most steel mills add a certain weight of slag modifiers to reduce the slag entering the ladle. These modifiers react chemically with the oxygen in the molten steel, consuming some of the oxygen. Some steel mills add aluminum shot, aluminum-manganese ferromanganese, and other aluminum-containing materials during tapping to pre-deoxidize the molten steel or slag.

[0004] RH stands for Refining Furnace. When smelting IF steel, the RH furnace primarily performs deep decarburization, final deoxidation, temperature fine-tuning, and alloying. In the RH process, the oxygen content of the molten steel is a crucial technical parameter, with different requirements at different stages. The oxygen content of the molten steel entering the RH furnace is closely related to the decarburization effect. If the oxygen content is too high, the oxygen content at the end of decarburization will be too high, ultimately affecting the cleanliness of the molten steel. If the oxygen content is too low, it will affect the decarburization effect. Furthermore, to ensure decarburization effectiveness, the oxygen content at the end of decarburization should not be too low, and to ensure steel cleanliness, the oxygen content at the end of decarburization should not be too high. Therefore, the oxygen content at the end of decarburization is generally controlled between 200-500 ppm. After decarburization, aluminum shot is added to perform deep deoxidation on the molten steel, ensuring that the oxygen content is less than 3 ppm before leaving the RH furnace. Continuous casting involves pouring the molten steel smelted in the RH refining furnace into continuously cast billets.

[0005] Different elements have varying deoxidizing capacities, and a deoxidation equilibrium exists, defined as the thermodynamic equilibrium of the reaction between dissolved oxygen in molten steel and the deoxidizing element to generate deoxidation products. According to metallurgical principles, the deoxidizing capacities of each element are in the following order: Al > Ti > Si > V > Cr > Mn. Therefore, considering both deoxidizing capacity and economic efficiency, Al, Si, and Mn are often chosen as deoxidizers. While aluminum-based deoxidizers offer good deoxidation effects, they are expensive, and their deoxidation product, Al2O3, easily causes nozzle blockage, leading to casting interruptions. It also causes the formation of inclusions with Al2O3 as their core in the steel. The reason for the nozzle blockage caused by aluminum-based deoxidizers is that Al2O3 has a high melting point in molten steel and exists in a solid state. It accumulates and grows on the inner wall of the nozzle along with other inclusions, eventually adhering to the nozzle wall and causing blockage.

[0006] Chinese patent CN105714010A discloses a converter silicon deoxidation method for IF steel and ultra-low carbon steel. The idea is to use ferrosilicon instead of ferroaluminum manganese for pre-deoxidation during the tapping process when smelting IF steel or ultra-low carbon steel, and it describes the timing of addition and the calculation method for the amount of ferrosilicon. However, its shortcomings are: it specifies a minimum tapping oxygen value, and this minimum value is too high. For example,

[0019] mentions that when bottom blowing is used, ferrosilicon can only be added for pre-deoxidation when the minimum tapping oxygen value is greater than 700 ppm, and it is not allowed to add ferrosilicon for pre-deoxidation when the tapping oxygen value is less than 700 ppm. Obviously, this process has stringent applicable conditions and is not frequently used in actual steelmaking production, resulting in poor cost reduction.

[0007] Chinese patent CN120400456A discloses a smelting method for silicon deoxidation of low-carbon, low-silicon aluminum-killed steel. The idea is to pre-deoxidize the molten steel by adding high-carbon ferromanganese and ferrosilicon deoxidizers sequentially during the tapping process, and then adding aluminum shot in the RH process for final deoxidation. This process reduces deoxidation and alloying costs to some extent. However, a problem exists: the amount of ferrosilicon added is too high, inevitably leading to excessive silicon content and requiring oxygen blowing for desiliconization in the RH process. This severely impacts RH production efficiency. Furthermore, this process is only suitable for low-carbon steel (0.01%–0.05%), and not for IF steel.

[0008] The aforementioned publicly available information indicates that in the current production practice of IF steel smelting, aluminum deoxidation is the main process. Although a small amount of research has been conducted on silicon deoxidation, the process has obvious defects. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a method for deoxidizing and alloying IF steel, employing a two-step pre-deoxidation process using ferrosilicon and a final deoxidation process using aluminum shot. This method not only reduces deoxidation costs but also improves the quality of molten steel.

[0010] The technical solution adopted in this invention is as follows:

[0011] This invention provides a method for deoxidizing and alloying IF steel, including converter smelting, RH refining and continuous casting. In the converter smelting step, lime is first added to the ladle in the later stage of tapping, and then ferrosilicon is added to pre-deoxidize the molten steel and ladle slag.

[0012] In the RH refining process, when the carbon content of the molten steel is qualified after decarburization, ferrosilicon is added for pre-deoxidation; after the ferrosilicon is added to the circulation, aluminum shot is added for deoxidation and alloying; after the aluminum shot is added to the circulation, alloy is added for alloying.

[0013] In the continuous casting process, the time interval between the start of continuous casting and the end of RH breaking is controlled to be ≤30min in order to reduce the secondary oxidation of molten steel.

[0014] In the converter smelting step, the amount of lime added is 2-5 kg / t of molten steel. The basis for determining the amount of lime is to thicken the slag, increase the slag viscosity, reduce the slag fluidity, and reduce the secondary oxidation of molten steel during the continuous casting process after the addition of RH to ferrosilicon.

[0015] In the converter smelting step, the amount of ferrosilicon added is 0.3-0.7 kg / t of molten steel; the basis for determining the amount of ferrosilicon is that even if all the Si in the ferrosilicon alloy enters the molten steel, it will not cause the Si content in the molten steel to exceed the upper limit of the steel grade.

[0016] In the converter smelting process, lime is added first, followed by ferrosilicon, when the weight of the molten steel in the ladle accounts for approximately 3 / 4 of the total weight of the molten steel in the furnace. Lime and ferrosilicon are added only in the later stages of tapping. This is because a considerable amount of converter slag has already entered the ladle in the later stages of tapping. The ferrosilicon added at this time can remove some of the oxygen from the slag. Furthermore, since tapping continues while lime and ferrosilicon are being added, the scouring effect of the steel flow on the added lime and ferrosilicon helps melt the lime and facilitates the chemical reaction between the ferrosilicon and the slag. According to the inventors' field experiments, adding lime and ferrosilicon when the weight of the molten steel in the ladle accounts for approximately 3 / 4 of the total weight of the molten steel in the furnace yields the best results.

[0017] In the RH refining step, oxygen is determined before RH pumping begins. The presence of C, Si, and oxygen content at the inlet determines whether oxygen blowing is required. If oxygen blowing is required, it is done through an oxygen lance. After oxygen blowing is completed, decarburization is performed.

[0018] In the RH refining step, the rule for determining whether oxygen blowing is required is: N 吹氧量 = (200 + 0.9 × [C]) RH进站 +1.142×[Si] RH进站 -[O] RH进站 ) ÷ 2, when N 吹氧量 When N > 0, oxygen blowing is required; when N 吹氧量 When N ≤ 0, oxygen blowing is not required; where N is the oxygen content of N.吹氧量 This refers to the oxygen blowing rate (RH), expressed in Nm³. 3 [O] RH进站 The oxygen concentration at the RH inlet is set in ppm [C]. RH进站 This refers to the carbon content of a steel sample taken from the ladle, expressed in ppm (parts per second). [Si] RH进站 The silicon content of the steel sample taken from the ladle is expressed in ppm.

[0019] In the RH refining step, the amount of ferrosilicon added is 0.05-0.10 kg / t of molten steel. If too much is added, the Si content of the molten steel will be too high when the RH breaks the air. If too little is added, less oxygen will be removed by the ferrosilicon. The circulation time after the addition of ferrosilicon is 1-2 min.

[0020] In the RH refining step, ferrosilicon is added to the circulation system for oxygen determination, and aluminum shot is added for final deoxidation and adjustment of the aluminum content in the molten steel.

[0021] In the RH refining step, aluminum shot used for final deoxidation and Als alloying is added and circulated for 3-4 minutes before alloying is added. After the alloy is added and circulated for 4-8 minutes, the furnace is ventilated, and the RH furnace smelting is completed.

[0022] The mass percentage of Si in ferrosilicon is 76-79%, C ≤ 0.015%, and the particle size of ferrosilicon is 5mm ≤ 35mm.

[0023] In converter smelting of IF steel, aluminum-containing modifiers are often added to deoxidize the slag during the tapping process. This inevitably removes some oxygen from the molten steel, producing deoxidation product Al2O3. In RH refining of IF steel, aluminum-containing materials such as aluminum shot and aluminum segments are used for final deoxidation of the molten steel. Most of the Al2O3 produced is removed through steel circulation, but some inevitably remains in the molten steel. Clearly, using only aluminum for deoxidation would result in a higher total oxygen content in the tundish steel.

[0024] Ferrosilicon deoxidation is commonly used in the smelting of special steels. However, because silicon's deoxidizing ability is weaker than aluminum's, some silicon remains in the molten steel after silicon deoxidation. Si is a harmful element for IF steel. Although silicon's deoxidizing ability is common knowledge in metallurgy, and previous studies have explored ferrosilicon deoxidation during the tapping process or RH refining process for other steel grades, no literature has yet publicly described the use of ferrosilicon deoxidation during converter tapping or RH refining deoxidation for IF steel. For this reason, the metallurgical industry uses aluminum deoxidation when smelting IF steel.

[0025] This invention develops a two-step ferrosilicon pre-deoxidation method (steel tapping silicon deoxidation, RH decarburization followed by silicon deoxidation) and a one-step aluminum final deoxidation method. Through scientific process design, it reduces deoxidation costs and the amount of Al2O3 deoxidation products in molten steel, thereby reducing the total oxygen content in the ladle and achieving a balance between cost reduction and quality improvement.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The deoxidation and alloying method for IF steel disclosed in this invention significantly reduces the cost of lime, modifiers, ferrosilicon and aluminum shot through scientific process design, and significantly reduces the total oxygen content in the intermediate liner. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of the deoxidation and alloying method for IF steel provided by the present invention. Detailed Implementation

[0029] This invention provides a method for deoxidizing and alloying IF steel, comprising converter smelting, RH refining, and continuous casting;

[0030] In the converter smelting process, 2-5 kg / t of lime is added to the ladle in the later stage of tapping, followed by 0.3-0.7 kg / t of ferrosilicon to pre-deoxidize the molten steel and ladle slag. After tapping, argon is blown for 2 minutes, and steel samples are taken from the ladle to analyze the carbon and Si content.

[0031] In the RH refining process, oxygen is determined before RH extraction begins. The presence of C, Si, and oxygen content at the inlet is used to determine whether oxygen blowing is necessary. If oxygen blowing is required, it is done using an oxygen lance. The rule for determining whether oxygen blowing is needed in RH is: N... 吹氧量 = (200 + 0.9 × [C]) RH进站 +1.142×[Si] RH进站 -[O] RH进站 ) ÷ 2, where N 吹氧量 RH oxygen blowing rate, Nm 3 [O] RH进站 The oxygen concentration at the RH inlet is determined in ppm (C). RH进站 The carbon content (ppm) and [Si] content of the steel sample taken from the ladle are given. RH进站 The silicon content (ppm) of a steel sample taken from the ladle is given when N... 吹氧量 When N > 0, oxygen needs to be purged. 吹氧量When the carbon content is ≤0, oxygen blowing is not required. After oxygen blowing, decarburization continues for a period of time. When the carbon content of the molten steel is qualified, 0.05-0.10 kg / t of ferrosilicon is added for pre-deoxidation. After adding ferrosilicon, the oxygen is fixed after 1-2 minutes of circulation. Aluminum shot is added for final deoxidation and Al alloying. After adding aluminum shot, the alloys such as ferrotitanium and ferroniobium are added for alloying after 3-4 minutes of circulation. After adding ferrotitanium and other alloys, the atmosphere is broken after 4-8 minutes of circulation. The RH furnace smelting is then completed.

[0032] Aluminum shot addition amount = weight of deoxidized aluminum shot + weight of alloyed aluminum shot, where, weight of deoxidized aluminum shot: 0.178 kg / t of aluminum is added for every 100 ppm of oxygen removed; weight of alloyed aluminum shot = amount of molten steel × target Al content / (aluminum content of aluminum shot * aluminum yield).

[0033] In the continuous casting process, after the RH refining is completed, the molten steel is continuously cast and poured. The time interval between the start of continuous casting and the end of RH degassing is controlled to be less than 30 minutes to reduce the secondary oxidation of the molten steel.

[0034] The composition and weight percentage of IF steel are shown in Table 1.

[0035] Table 1

[0036]

[0037] The other element is Fe.

[0038] The present invention will now be described in detail with reference to embodiments and comparative examples.

[0039] The main components of the modifier used in the comparative examples are: TAl: ≥45%, Al2O3: 25-35%, SiO2 ≤8%, CaCO3: 5-10%. Comparative examples 1 and 2 used the same batch of modifier.

[0040] Example 1

[0041] The target weight percentage of IF steel produced using the "converter smelting-RH refining-continuous casting" process is shown in Table 2.

[0042] Table 2

[0043]

[0044] The other element is Fe.

[0045] The nominal capacity of the converter is 300 tons, and the actual amount of molten steel produced is about 310 tons.

[0046] Converter smelting: After converter blowing, the molten steel is tapped once its temperature and composition meet the requirements. When 3 / 4 of the steel has been tapped, 1200 kg of lime is added to the ladle. After the lime addition is complete, 120 kg of ferrosilicon is added. The ferrosilicon has a Si content of 78% and a C content of 0.008%, with a particle size of 5mm ≤ 35mm and a pass rate of ≥ 95%. To avoid lime and ferrosilicon accumulating on the surface of the molten steel, it is preferable to add the lime and ferrosilicon to the ladle via a rotary chute.

[0047] Two minutes after the steel was purged with argon, a steel sample was taken from the ladle to analyze the carbon and Si content. The actual analytical values ​​were 240 ppm and 110 ppm, respectively.

[0048] RH refining: Before starting RH extraction, the oxygen content is set at 475 ppm. Whether oxygen blowing is needed is determined based on the C, Si, and oxygen content at the inlet.

[0049] N 吹氧量 = (200 + 0.9 * [C]) RH进站 +1.142[Si] RH进站 -[O] RH进站 )2=(200+0.9*240+1.142*110-475)=33Nm 3 ;

[0050] Due to N 吹氧量 =33Nm 3 >0. To ensure effective RH decarburization, oxygen blowing is required. Therefore, after starting the extraction, 33 Nm of oxygen is blown through an oxygen lance. 3 Using RH general technology, after oxygen blowing, the carbon content of the molten steel reaches 13 ppm when the steel is circulated for 11 minutes. At this time, 25 kg of ferrosilicon is added to pre-deoxidize the molten steel. After 2 minutes of circulation following the addition of ferrosilicon, the oxygen content is stabilized at 191 ppm. 239 kg of aluminum shot is added for final deoxidation and Al alloying. After 3 minutes of circulation following the addition of aluminum shot, electrolytic manganese, ferrotitanium, and ferroniobium are added for alloying. After 5 minutes of circulation following the addition of ferrotitanium, ferroniobium, and other alloys, the atmosphere is broken, and the RH furnace smelting is completed.

[0051] After the RH cavitation system is broken, the molten steel is hoisted to the continuous casting station for pouring, and the time interval between the start of continuous casting and the end of the RH cavitation system break is controlled to be 25 minutes.

[0052] Comparative Example 1

[0053] The target weight percentage of IF steel produced using the "converter smelting-RH refining-continuous casting" process is shown in Table 3.

[0054] Table 3

[0055]

[0056] The other element is Fe.

[0057] The nominal capacity of the converter is 300 tons, and the actual amount of molten steel produced is about 314 tons.

[0058] Converter smelting: After converter blowing, the molten steel is tapped when the temperature and composition are qualified. After tapping, 350 kg of modifier is added to the ladle to modify the slag. Inevitably, the molten steel is also partially deoxidized. One minute after tapping, argon is blown into the ladle, and steel samples are taken to analyze the carbon content. The actual analysis value is 263 ppm.

[0059] RH refining: Before starting RH extraction, the oxygen content was set at 416 ppm. Based on the incoming carbon and oxygen content, 72 Nm³ of oxygen was blown in, according to experience. 3 14 minutes after the oxygen blowing ends, the carbon content of the molten steel reaches 12 ppm, and the oxygen content is 352 ppm. 323 kg of aluminum shot is added for final deoxidation and Al alloying. After the aluminum shot is added and circulated for 4 minutes, electrolytic manganese, ferrotitanium, and ferroniobium are added for alloying. After the ferrotitanium, ferroniobium, and other alloys are added and circulated for 6 minutes, the atmosphere is broken, and the RH furnace smelting ends.

[0060] After the RH breaks through the vent, the molten steel is hoisted to the continuous casting stage. The time interval between the start of continuous casting and the end of the RH breaking through the vent is 31 minutes.

[0061] Example 2

[0062] The target weight percentage of IF steel produced using the "converter smelting-RH refining-continuous casting" process is shown in Table 4.

[0063] Table 4

[0064]

[0065] The other element is Fe.

[0066] The nominal capacity of the converter is 300 tons, and the actual amount of molten steel produced is about 307 tons.

[0067] Converter smelting: After converter blowing, the molten steel is tapped once its temperature and composition meet the requirements. When 3 / 4 of the steel has been tapped, 900 kg of lime is added to the ladle. After the lime addition is complete, 202 kg of ferrosilicon is added. The ferrosilicon alloy has Si: 76%, C: 0.007%, and the qualified rate of ferrosilicon particles with a size of 5mm ≤ 35mm is ≥ 95%. To avoid lime and ferrosilicon accumulating on the surface of the molten steel, it is preferable to add the lime to the ladle via a rotary chute.

[0068] Two minutes after the steel was purged with argon, a steel sample was taken from the ladle to analyze the carbon and Si content. The actual analytical values ​​were 316 ppm and 170 ppm, respectively.

[0069] RH refining: Before starting RH extraction, the oxygen content is set at 728 ppm. Whether oxygen blowing is needed is determined based on the C, Si, and oxygen content at the inlet.

[0070] N 吹氧量 = (200 + 0.9 * [C]) RH进站 +1.142[Si] RH进站 -[O] RH进站 )÷2=(200+0.9*316+1.142*170-728)÷2=-24.7Nm 3 ; Due to N 吹氧量 ==-24.7Nm 3 Since the carbon content is less than 0, deep decarburization can be guaranteed without oxygen blowing. Using the general RH technology, the carbon content of the molten steel reaches 15 ppm after 16 minutes of RH pumping. At this time, 31 kg of ferrosilicon is added to pre-deoxidize the molten steel. After 2 minutes of circulation following the addition of ferrosilicon, the oxygen content is stabilized at 224 ppm. 257 kg of aluminum shot is then added for final deoxidation and Al alloying. After 4 minutes of circulation following the addition of aluminum shot, electrolytic manganese and ferrotitanium are added for alloying. After 7 minutes of circulation following the addition of the electrolytic manganese and ferrotitanium alloy, the atmosphere is broken, and the RH furnace smelting is completed.

[0071] After the RH cavitation system is broken, the molten steel is hoisted to the continuous casting station for pouring, and the time interval between the start of continuous casting and the end of the RH cavitation system break is controlled to be 22 minutes.

[0072] Comparative Example 2

[0073] The target weight percentage of IF steel produced using the "converter smelting-RH refining-continuous casting" process is shown in Table 5.

[0074] Table 5

[0075]

[0076] The other element is Fe.

[0077] The converter has a nominal capacity of 300 tons, but the actual amount of molten steel produced is about 298 tons.

[0078] Converter smelting: After converter blowing, the molten steel is tapped when the temperature and composition are qualified. After tapping, 402 kg of modifier is added to the ladle to modify the slag. Inevitably, the molten steel is also partially deoxidized. One minute after tapping, argon is blown into the ladle, and steel samples are taken to analyze the carbon content. The actual analysis value is 228 ppm.

[0079] RH refining: Before RH furnace pumping, oxygen content is determined to be 624 ppm. Based on the carbon and oxygen content at the inlet, oxygen blowing is not required according to experience. 15 minutes after RH furnace pumping starts, the carbon content of the molten steel reaches 13 ppm, and oxygen content is determined to be 396 ppm. 346 kg of aluminum shot is added for final deoxidation and Al alloying. After the aluminum shot is added and circulated for 4 minutes, electrolytic manganese and ferrotitanium are added for alloying. After the electrolytic manganese and ferrotitanium are added and circulated for 6 minutes, the atmosphere is broken, and RH furnace smelting ends.

[0080] After the RH breaks through the vent, the molten steel is hoisted to the continuous casting station for pouring. The time interval between the start of continuous casting and the end of the RH breaking through the vent is 33 minutes.

[0081] Comparative Example 3

[0082] IF steel was smelted using the "converter smelting-RH refining-continuous casting" process, and the target weight percentage of the IF steel produced is shown in Table 5.

[0083] The nominal capacity of the converter is 300 tons, and the actual amount of molten steel produced is about 301 tons.

[0084] Converter smelting: After converter blowing, the molten steel is tapped once its temperature and composition meet the requirements. When 3 / 4 of the steel has been tapped, 1043 kg of lime is added to the ladle. After the lime addition is complete, 110 kg of ferrosilicon is added. The ferrosilicon has a Si content of 78% and a C content of 0.008%, with a particle size of 5mm ≤ 35mm and a pass rate of ≥ 95%. To avoid lime and ferrosilicon accumulating on the surface of the molten steel, it is preferable to add the lime to the ladle via a rotary chute.

[0085] Two minutes after the steel was purged with argon, a steel sample was taken from the ladle to analyze the carbon and Si content. The actual analytical values ​​were 275 ppm and 98 ppm, respectively.

[0086] RH refining: Before starting RH extraction, the oxygen content is determined to be 628 ppm. Whether oxygen blowing is needed is determined based on the C, Si, and oxygen content at the inlet.

[0087] N 吹氧量 = (200 + 0.9 * [C]) RH进站 +1.142[Si] RH进站 -[O] RH进站 )2=(200+0.9*275+1.142*98-628)=-68Nm 3 ; Due to N 吹氧量 =-68Nm 3Since the carbon content is less than 0, deep decarburization can be guaranteed without oxygen blowing. Using the general RH technology, the carbon content of the molten steel reaches 14 ppm after 15 minutes of RH pumping. At this time, 90 kg of ferrosilicon is added to pre-deoxidize the molten steel. After 2 minutes of circulation following the addition of ferrosilicon, the oxygen content is stabilized at 248 ppm. 242 kg of aluminum shot is then added for final deoxidation and Al alloying. After 4 minutes of circulation following the addition of aluminum shot, electrolytic manganese and ferrotitanium are added for alloying. After 7 minutes of circulation following the addition of the electrolytic manganese and ferrotitanium alloy, the atmosphere is broken, and the RH furnace smelting is completed.

[0088] After the RH cavitation system is broken, the molten steel is hoisted to the continuous casting station for pouring, and the time interval between the start of continuous casting and the end of the RH cavitation system break is controlled to be 28 minutes.

[0089] The RH void composition is shown in Table 8. Among them, the Si content is 0.012%, which exceeds the upper limit of 0.010%.

[0090] The main parameters in the above embodiments and comparative examples are shown in Table 6 below.

[0091] Table 6

[0092]

[0093] (Continued from the table above)

[0094]

[0095] The cost of raw materials used in the above embodiments and comparative examples is summarized in Table 7.

[0096] Table 7

[0097]

[0098] The chemical composition and weight percentage of the IF steel smelted in the above embodiments and comparative examples are shown in Table 8.

[0099] Table 8

[0100]

[0101] As can be seen from the table above, compared with Comparative Example 1, the cost of lime + modifier + ferrosilicon + aluminum shot in Example 1 was reduced by 9.63 yuan / t of steel, and the total oxygen in the intermediate ladle was reduced by 1.8 ppm.

[0102] Compared to Comparative Example 2, Example 2 reduced the cost of lime + modifier + ferrosilicon + aluminum shot by 10.11 yuan / t steel and reduced the total oxygen content in the intermediate ladle by 1.4 ppm.

[0103] In Comparative Example 3, the large amount of ferrosilicon added for pre-deoxidation resulted in the Si content at the RH outlet reaching 0.012%, which exceeded the upper limit (0.010%).

[0104] The above detailed description of a method for deoxidizing and alloying IF steel with reference to the embodiments is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for deoxidizing and alloying IF steel, comprising converter smelting, RH refining, and continuous casting, characterized in that: In the converter smelting process, lime is added to the ladle first in the later stage of tapping, followed by ferrosilicon to pre-deoxidize the molten steel and ladle slag. In the RH refining process, when the carbon content of the molten steel is qualified after decarburization, ferrosilicon is added for pre-deoxidation; after the ferrosilicon is added to the circulation, aluminum shot is added for deoxidation and alloying; after the aluminum shot is added to the circulation, alloy is added for alloying. During the continuous casting process, the time interval between the start of continuous casting and the end of RH cavitation should be controlled to be ≤30min.

2. The method for deoxidizing and alloying IF steel according to claim 1, characterized in that: In the converter smelting step, the amount of lime added is 2-5 kg / t of molten steel.

3. The method for deoxidizing and alloying IF steel according to claim 1, characterized in that: In the converter smelting step, the amount of ferrosilicon added is 0.3-0.7 kg / t of molten steel.

4. The method for deoxidizing and alloying IF steel according to claim 1, characterized in that: In the converter smelting process, when the weight of the molten steel in the ladle accounts for about 3 / 4 of the total weight of the molten steel in the furnace, lime is added first, followed by ferrosilicon.

5. The method for deoxidizing and alloying IF steel according to claim 1, characterized in that: In the RH refining step, oxygen is determined before RH pumping begins. The presence of C, Si, and oxygen content at the inlet determines whether oxygen blowing is required. If oxygen blowing is required, it is done through an oxygen lance. After oxygen blowing is completed, decarburization is performed.

6. The method for deoxidizing and alloying IF steel according to claim 4, characterized in that: In the RH refining step, the rule for determining whether oxygen blowing is required is: N 吹氧量 = (200 + 0.9 × [C]) RH进站 +1.142×[Si] RH进站 -[O] RH进站 ) ÷ 2, when N 吹氧量 When N > 0, oxygen blowing is required; when N 吹氧量 When the oxygen level is ≤0, oxygen blowing is not required; In the formula, N 吹氧量 This refers to the oxygen blowing rate (RH), expressed in Nm³. 3 [O] RH进站 The oxygen concentration at the RH inlet is set in ppm [C]. RH进站 This refers to the carbon content of a steel sample taken from the ladle, expressed in ppm (parts per second). [Si] RH进站 The silicon content of the steel sample taken from the ladle is expressed in ppm.

7. The method for deoxidizing and alloying IF steel according to any one of claims 1-6, characterized in that: In the RH refining step, the amount of ferrosilicon added is 0.05-0.10 kg / t of molten steel, and the circulation time after the addition of ferrosilicon is 1-2 min.

8. The method for deoxidizing and alloying IF steel according to any one of claims 1-6, characterized in that: In the RH refining step, ferrosilicon is added to the circulation system for oxygen determination, and aluminum shot is added for final deoxidation and adjustment of the aluminum content in the molten steel.

9. The method for deoxidizing and alloying IF steel according to any one of claims 1-6, characterized in that: In the RH refining step, aluminum shot used for final deoxidation and Als alloying is added and circulated for 3-4 minutes before alloying is added. After the alloy is added and circulated for 4-8 minutes, the furnace is ventilated, and the RH furnace smelting is completed.

10. The method for deoxidizing and alloying IF steel according to any one of claims 1-6, characterized in that: The mass percentage of Si in ferrosilicon is 76-79%, C ≤ 0.015%, and the particle size of ferrosilicon is 5mm ≤ 35mm.

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