Method for reducing oxidability of steelmaking endpoint slag and oxygen activity of molten steel [O]

Abstract

The invention discloses a method for reducing the oxidability of steelmaking endpoint slag and the oxygen activity of molten steel [O], and belongs to the field of steelmaking. According to the process method, the reducing agent is added into the furnace from the overhead bunker before the gun is lifted to stop blowing or while the gun is lifted to stop blowing at the blowing end point, the process is simple and convenient to implement, the existing process steps are not changed, the smelting and auxiliary time is not occupied, and the cheap reducing agents such as anthracite, coke, semi-coke and waste magnesia carbon brick particles can be used; the effects of reducing the oxidability of the end-point slag, namely the content of (sigma FeO) and reducing the [O] activity of the molten steel are good; the silicon-containing reducing agent is used, so that the oxygen activity of molten steel [O] and in slag (sigma FeO) can be greatly reduced, the consumption of a deoxidizing agent is reduced, a reaction product (SiO2) is beneficial to slagging and dephosphorization of low-silicon molten iron and semi-steel, and rephosphorization of the molten steel is avoided; the consumption of a deoxidizing agent is reduced, and the quality of the molten steel is improved.

Description

Technical Field

[0001] The invention relates to the field of steelmaking, and in particular to a simple method for reducing the oxidizability of steelmaking end-point slag. Background Art

[0002] At the end of steelmaking blowing, the slag oxidation, i.e., the (∑FeO) content, varies. Generally, the end slag (∑FeO) content of medium and high carbon steels is low, while the end slag (∑FeO) content of low carbon, ultra-low carbon steels, semi-steel and post-blowing furnaces is high. When the end slag (∑FeO) content is high, the oxidation of the molten steel, i.e., the oxygen activity of [O], is high, the deoxidizer and alloy consumption in the ladle during steelmaking is large, and the internal inclusions of the steel are more, which directly affects the quality of the steel; when the end slag (∑FeO) content is high, the metal recovery rate is low, the slag is thin, and it is not easy to block the slag and splash the slag to protect the furnace.

[0003] When the converter stops blowing and the oxygen lance is lifted, the oxygen can only be turned off when the oxygen lance is lifted to the oxygen shut-off point above the converter mouth. It takes 5-10 seconds for the oxygen lance to be lifted to the oxygen shut-off point above the converter mouth. The oxygen supply intensity is 2.0-4.0m3 / min.t when the lance is lifted. 钢 According to calculations, the oxygen supplied during this period can increase the final slag (∑FeO) content in the molten pool by about 1.0-5.0%, and the oxygen still injected into the molten pool before the blowing is stopped only continues to increase the (∑FeO) in the slag and accumulates [O] activity in the molten steel. According to calculations, for every 1% increase in the final slag (FeO), the molten steel [O] increases by about 50ppm, which will subsequently increase the deoxidizer consumption and the inclusions in the molten steel.

[0004] In order to reduce the (∑FeO) in the final slag and reduce the oxidizability of molten steel, i.e., the [O] oxygen activity, professional technicians have developed a number of processes, such as a patented method for controlling ultra-low iron oxide in converter final slag (CN202110444029.9). This process is complex. Compared with the original process, this process method reduces the (∑FeO) in the final slag by 1.99%.

[0005] In order to reduce the consumption of aluminum deoxidizer in the ladle during steel tapping, coal-based recarburizer is added to the ladle for pre-deoxidation during the steel tapping process, such as a low-cost deoxidation process for low-carbon steel tapping in a converter (CN201710302904.3); the patent application "A method and system for deoxidizing molten steel during steel tapping from a converter (CN202410033760.6)" also adds the first deoxidizer, coke powder, during steel tapping.

[0006] In addition, the early stage of the converter blowing temperature is low, the distribution ratio of phosphorus in slag and iron is large, and the early stage of blowing is more suitable for dephosphorization. For low-silicon molten iron with [Si] < 0.4%, in the early stage of blowing, due to the low mass fraction of silicon in the molten iron, the manganese element in the molten iron is completely oxidized within 1 to 2 minutes, the molten iron chemically releases less heat, the molten pool heats up slowly in the early stage, the amount of lime added is small and difficult to melt, the acidic oxide SiO content in the slag is low, and the solid phosphorus phase 2CaOSiO2 formed is small, resulting in missing the favorable opportunity for dephosphorization at the low temperature stage.

[0007] The silicon content in the molten iron is low, and the blowing enters the carbon-oxygen reaction period early. At this time, the decarburization speed is very high. The oxygen blown in and the iron oxide in the slag are used to participate in the decarburization reaction, so that the (FeO) content in the slag reaches the lowest value. The (FeO) content in the slag is reduced, resulting in the high melting point dicalcium silicate phase that wraps the lime, making the lime difficult to melt. The amount of slag generated is small, and the slag layer cannot cover the molten steel well. The exposed molten steel and slag are very likely to stick to the steel and the smoke hood under the action of the oxygen jet, and the degree of drying in the middle of smelting is aggravated. As the decarburization reaction continues, the temperature of the molten pool increases, the carbon content in the steel gradually decreases, and the (FeO) content in the slag increases. Entering the late stage of blowing, the decarburization reaction slows down, the stirring of the molten pool weakens, and the temperature rises to melt the lime, but it does not have time to fully react, and it reaches the end of blowing. The high-basicity oxidizing slag formed at this time has a small amount of slag and insufficient dephosphorization capacity, resulting in high oxidation and phosphorus content in the terminal slag.

[0008] In order to make up for the shortage of low-silicon molten iron, a patent for converter smelting of low-silicon molten iron (CN202210817710.8) is to add 15-25% high-silicon molten iron containing 1.6-1.9% [Si] to the low-silicon molten iron to make up for the shortage of [Si] in the low-silicon molten iron; a patent for a method for solving the difficulty of slagging in converter smelting ultra-low silicon molten iron (CN202310578009.X) is to add ladle slag with acidic components of SiO2 and Al2O3 at the early stage of blowing.

[0009] After the vanadium extraction process, the semi-steel poured out contains traces of [Si] and [C] of 0.30-3.8%. Therefore, in the process of smelting semi-steel, there are fewer acidic slag-forming substances, the initial slag is formed late, and the chemical heat generated by the molten iron is insufficient, which makes it more difficult to use semi-steel to make steel than low-silicon molten iron, and the dephosphorization rate is low. Due to the lack of elements such as [Si] and [Mnn] in semi-steel, the initial slag of the converter is formed slowly, with an average formation time of about 3 and a half minutes. When the slag is discharged in the early stage of the converter, the initial slag is just formed and has not fully participated in the dephosphorization reaction; at the end of the dephosphorization period, when the carbon-oxygen reaction is intense, the slag is seriously foamed, the slag is difficult to pour, and the steel material is seriously lost during the slag pouring process; due to the heat loss in the vanadium extraction process, the heat of semi-steel steelmaking is insufficient, and the slag discharge in the early stage of the converter further increases the heat loss. In order to melt lime and dephosphorize, the late stage of smelting mainly relies on iron oxidation to increase heat energy, so a high-basicity, high-oxidizing terminal slag is formed, and the oxidation of the molten steel, that is, the [O] oxygen activity, is greatly increased. A series of technologies have been developed for this purpose, such as the patent application "Method for reducing the oxygen activity of molten steel at the end point of semi-steel smelting" (CN201610035307.4).

[0010] Patents for a method for slag making of semi-steel (CN201410250194.0) and a method for reducing the consumption of auxiliary materials for semi-steel steelmaking (CN201810177350.3) both involve adding ferrosilicon alloy to semi-steel to increase the acidic oxide (SiO2) content in the slag and raise the temperature of the molten pool, but the smelting cost of this process is too high.

[0011] From a cost perspective, the lower the (FeO) content in the final slag, the better. However, if the (FeO) content in the final slag is too low, such as (FeO) < 15%, it is easy to cause the final molten steel to rephosphorize. At this time, (FeO) powder must be added to increase the (FeO) content in the slag to ensure that the (FeO) in the slag is > 15%. For details, see the patent "A method for reducing the amount of rephosphorization in the converter steelmaking process-(CN201010260158.4). This limits the further reduction of the oxidizability of the final slag and the benefits brought by it. Summary of the invention

[0012] In view of the series of problems existing above, during the oxygen lance lifting process at the end of converter blowing, the oxygen sprayed by the oxygen lance increases the end slag (∑FeO) and when the blowing is stopped, the oxygen sprayed into the molten pool causes the molten steel to accumulate [O] activity exceeding the equilibrium with carbon, and the above-mentioned problems, the present invention aims to develop a method for reducing the oxidizability of the steelmaking end slag and the [O] oxygen activity of molten steel, so as to reduce the (∑FeO) in the end slag and the [O] activity in the molten steel.

[0013] The technical solution of the method for reducing the oxidizability of slag at the end of steelmaking and the oxygen activity of molten steel [O] is as follows: blowing is carried out according to the standard operating process of different steel grades, and before the blowing is stopped or while the gun is raised at the end of blowing, a reducing agent is added into the furnace from a high-level silo.

[0014] Furthermore, before the first blowing end is to be stopped or while the gun is being raised, reducing agent is added into the furnace from a high-level silo. If the molten steel is unqualified, supplementary blowing is performed. After the supplementary blowing is completed, before the second blowing end is to be stopped or while the gun is being raised, reducing agent is again added into the furnace from a high-level silo.

[0015] Furthermore, adding the reducing agent into the furnace from the high-level silo before or while the lance is being raised and blowing is stopped means ensuring that the reducing agent added from the high-level silo completely falls into the molten pool before the oxygen lance is being raised or when the oxygen lance is just being raised.

[0016] Furthermore, the reducing agent is one or two of a carbon-containing reducing agent, a silicon-containing reducing agent, an aluminum-containing reducing agent, and a calcium-containing reducing agent.

[0017] Furthermore, the carbon-containing reducing agent is one of coke particles, bituminous coal particles, anthracite particles, semi-coke particles, high-carbon coal gangue particles, and waste magnesium carbon brick particles.

[0018] Furthermore, the silicon-containing reducing agent is one of silicon mud balls, silicon carbide particles, ferrosilicon particles, and calcium silicon particles.

[0019] Furthermore, the aluminum-containing reducing agent is one of aluminum particles and aluminum ash balls.

[0020] Furthermore, the calcium-containing reducing agent is calcium carbide.

[0021] Furthermore, the reducing agent is added in an amount of 0.2-5 kg / t steel.

[0022] The principle of the technical solution of the present invention is that the [O] in the molten steel at the end of blowing of all steel grades far exceeds the carbon-oxygen equilibrium point. The oxygen concentration in the molten steel at the end of blowing can be expressed as: [%O] = [O] balance + △ [O], where [O] balance is the oxygen concentration under the carbon-oxygen equilibrium state, and △ [O] is the degree of peroxidation or excess oxygen concentration in the molten steel. Generally, the higher the (ΣFeO) content in the end slag, the greater the △ [O] in the molten steel, and vice versa. △ [O] is also related to [C]. The lower the [C] in the molten steel, the greater the △ [O]. Low-carbon steel grades, semi-steel and post-blowing furnaces have a high content of (ΣFeO) in the end slag, so there is more excess △ [O] at the end of the molten pool.

[0023] At the moment when blowing is stopped, since the [O] in the molten steel at the end of blowing for all steel grades is far above the carbon-oxygen equilibrium point, the oxygen that is still being sprayed into the molten pool only continues to increase the (∑FeO) in the slag and accumulates [O] activity in the molten steel. During the lifting process of the oxygen lance at the end of converter blowing, the oxygen sprayed from the oxygen lance also further increases the end slag (ΣFeO), especially when low-silicon molten iron, semi-steel smelting, and post-blowing furnaces are used, the [O] activity and end slag (ΣFeO) of the molten steel are higher.

[0024] Before the planned stop of blowing or while the gun is being lifted, C, especially SiC and other Si-containing reducing agents, are added from the high-level silo. The reducing agents entering the molten pool react quickly with the oxygen jet under the impact of the oxygen jet. The oxygen sprayed in the process of lifting the gun acts more on the reducing agent, preventing the oxygen from further oxidizing the metallic iron. On the other hand, the surplus reducing agent is quickly mixed with the molten steel pool under the impact of the oxygen jet, and directly undergoes redox reaction with △[O] in the molten steel in the molten pool and (∑FeO) in the slag, which not only prevents the increase of the (∑FeO) content in the slag during the process of lifting the gun, but also reduces the activity of the original (∑FeO) in the slag and the △[O] in the molten steel.

[0025] The use of Si-containing reducing agents not only adds a large amount, but also can deeply reduce the oxygen activity of molten steel [O] and the condition of (∑FeO) in slag, and the molten steel is not easy to increase carbon. Taking anthracite and SiC as reducing agents as an example, the following reaction occurs:

[0026] 2C+O2=2CO↑ (1)

[0027] C+O2=CO2↑ (2)

[0028] C+(FeO)=Fe+CO↑ (3)

[0029] C+[O]=CO↑ (4

[0030] SiC+O2=SiO2+CO2↑ (5)

[0031] SiC+2(FeO)=2Fe+SiO2+CO2↑ (6)

[0032] SiC+3[O]=SiO2+CO↑ (7)

[0033] 2fCaO+SiO2=2CaO.SiO2 (8)

[0034] In the above reaction, if anthracite is used as a reducing agent, if too much is added, the molten steel is prone to carbonization and may cause the molten steel to return to phosphorus, thereby limiting the reduction of the oxygen activity of the molten steel [O] and the reduction of (∑FeO) in the slag; while using SiC as a reducing agent, the oxygen activity of the molten steel [O] and the (∑FeO) in the slag can be further reduced. After the reaction product SiO2 enters the slag, it can not only digest the free calcium oxide fCaO in the slag, but also form more 2CaO.SiO2 with it, thereby increasing the solid phosphorus phase in the slag; using CaC2 as a reducing agent Original agent, CaO is formed in the slag after deoxidation; the use of SiC or CaC2 reducing agent can both prevent the rephosphorization of molten steel due to excessive reduction of (ΣFeO); the converter implements slag retention operation, and using CaC2 as a reducing agent can reduce the amount of lime for the next furnace; and using SiC as a reducing agent can provide more acidic component SiO2 for the next furnace of low-silicon molten iron or semi-steel smelting, reducing or eliminating ferrosilicon or acidic oxides (SiO2), which is beneficial to the slag dephosphorization and slag splashing furnace protection operations of low-silicon molten iron and semi-steel.

[0035] Beneficial Effects

[0036] The invention discloses a method for reducing the oxidizability of steelmaking terminal slag and the oxygen activity of molten steel. The method has the advantages of simple process and convenient implementation, does not change the existing process steps, does not occupy smelting and auxiliary time, can use cheap reducing agents such as anthracite, coke, semi-coke and coal dry stone, and has good effects of reducing the oxidizability of terminal slag, i.e., the content of (∑FeO) and reducing the oxygen activity of molten steel; improves the yield of molten steel, reduces the consumption of deoxidizer, and improves the quality of molten steel.

[0037] If a silicon-containing reducing agent is used at the end point, the oxygen activity of molten steel [O] and the slag (∑FeO) can be greatly reduced, which not only reduces the deoxidizer consumption, but the reaction product (SiO2) is beneficial to the slag dephosphorization of low-silicon molten iron and semi-steel, and is also beneficial to the slag retention and slag making operation of the next furnace.

[0038] Using CaC2 as a reducing agent can reduce the amount of lime used in the next furnace.

[0039] The use of high-carbon coal gangue or aluminum ash balls at the end of the medium and high-carbon steel furnace not only reduces the (∑FeO) content in the slag and the [O] activity of the molten steel, but also increases the Al2O3 content in the slag, ensuring a certain fluidity of the slag. DETAILED DESCRIPTION

[0040] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this implementation. On the contrary, the purpose of introducing the invention in conjunction with the implementation is to cover other options or modifications that may extend based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0042] The present invention discloses a method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel. According to different molten iron conditions and steel grade requirements, blowing is performed according to operating specifications. When the blowing is to be stopped by lifting the gun or while lifting the gun and stopping the blowing at the end of blowing, a reducing agent is added into the furnace from a high-level silo. The amount of reducing agent added is selected according to the amount of end slag and the oxidizability. The amount of reducing agent added is 0.2-5kg / t steel. Generally, the amount of end slag is small or the oxidizability is weak, and the amount added is a low value, otherwise the amount added is a high value.

[0043] Example 1

[0044] 120t converter.

[0045] Smelting steel grade: X65.

[0046] The reducing agent is anthracite (C 93%) with a particle size of 10-20 mm.

[0047] After adding scrap steel and molten iron to the converter, it is blown normally, with an oxygen supply intensity of 4.0m3 / (min·t steel), a bottom blowing air supply intensity of 0.025m3 / (min·t steel), and a blowing oxygen lance position of 1.25m. When the oxygen blowing progress of the top oxygen lance is 90%, the oxygen supply intensity of the top oxygen lance is reduced to 2.2m3 / (min·t steel), and the oxygen lance height is raised to 1.9m until the oxygen blowing is completed. Before stopping the oxygen blowing and raising the lance, add 60kg of anthracite into the converter from the high-level silo. After stopping the blowing, take samples for testing, slag and steel are discharged, and the following are obtained:

[0048] The final slag (∑FeO) content is 20%, the final molten steel [C] content is 0.035%, and the molten steel oxygen activity is 805ppm.

[0049] Example 2

[0050] 120t converter.

[0051] Smelting steel grade: X65.

[0052] The reducing agent is anthracite (C 93%) with a particle size of 20-30 mm.

[0053] After adding scrap steel and molten iron to the converter, it is blown normally. The oxygen supply intensity is 3.5m3 / (min·t steel), the bottom blowing gas supply intensity is 0.05m3 / (min·t steel), and the blowing oxygen lance position is 1.4m. When the oxygen blowing progress of the top oxygen lance is 93%, the oxygen supply intensity of the top oxygen lance is reduced to 2.2m3 / (min·t steel), and the oxygen lance height is raised to 1.9m until the oxygen blowing is completed. Before stopping the oxygen blowing and raising the lance, 100kg of anthracite is added to the converter from the high-level silo. After stopping the blowing, the molten steel [C] is measured to be high, and the blowing is supplemented for 20S. After the supplementary blowing, while stopping the oxygen blowing and raising the lance, 140kg of anthracite is added to the converter from the high-level silo for sampling and testing, slag discharge, and steel discharge, and the following is obtained:

[0054] The final slag (∑FeO) content is 17%, the final molten steel [C] content is 0.004%, and the molten steel oxygen activity is 650ppm.

[0055] Example 3

[0056] 120t converter.

[0057] Smelting steel grade: X65.

[0058] The reducing agent is silicon carbide with a particle size of 10-20 mm (including 72% SiC).

[0059] After adding molten iron to the converter, the oxygen supply intensity is 4.0m3 / (min·t steel), the bottom blowing air supply intensity is 0.025m3 / (min·t steel), and the blowing oxygen lance position is 1.25m. When the oxygen blowing progress of the top oxygen lance is 90%, the oxygen supply intensity of the top oxygen lance is reduced to 2.2m3 / (min·t steel), and the oxygen lance height is raised to 1.9m until the oxygen blowing is completed. Before stopping the oxygen blowing and raising the lance, add 250kg of silicon carbide into the converter from the high-level silo. After stopping the blowing, take samples for testing, slag and steel are discharged, and the following are obtained:

[0060] The final slag (∑FeO) content is 14%, the final molten steel [C] content is 0.035%, and the molten steel oxygen activity is 505ppm.

[0061] The molten steel does not rephosphorize.

[0062] Example 4

[0063] 120t converter.

[0064] Smelting steel grade: X65.

[0065] The reducing agent is silicon carbide with a particle size of 10-20 mm (containing 72% SiC).

[0066] After the converter is added with low silicon iron water ([Si] 0.25%), it is blown normally, with oxygen supply intensity of 4.0m3 / (min·t steel), bottom blowing gas supply intensity of 0.025m3 / (min·t steel), blowing oxygen lance position of 1.25m, when the oxygen blowing progress of the top oxygen lance is 90%, the oxygen supply intensity of the top oxygen lance is reduced to 2.2m3 / (min·t steel), and the oxygen lance height is raised to 1.9m until the oxygen blowing is completed. Before stopping the oxygen blowing and raising the lance, 350kg of silicon carbide is added to the converter from the high-level silo. After stopping the blowing, sampling and testing, slag discharge, and steel discharge are obtained:

[0067] The final slag (∑FeO) content is 11, the final molten steel [C] content is 0.035%, and the molten steel oxygen activity is 362ppm.

[0068] The molten steel does not rephosphorize.

[0069] Example 5

[0070] 120t converter.

[0071] Metallurgical steel type: 65# spring steel.

[0072] The reducing agent is high carbon coal dry stone (C 20%) with a particle size of 10-20 mm.

[0073] The converter adopts normal blowing after adding scrap steel and molten iron, the oxygen supply intensity is 4.0m3 / (min·t steel), the bottom blowing gas supply intensity is 0.025m3 / (min·t steel), the blowing oxygen lance is at 1.4m, and the lance is raised to 1.8m when the oxygen blowing reaches 95%, and the bomb is dropped to measure the pouring time of 11min56s. When the blowing reaches 11min56s (excluding the slag pouring time), the blowing is stopped and the lance is raised. At the same time as the oxygen blowing is stopped and the lance is raised, 350kg of high-carbon dry coal stone is added to the converter from the high-level silo. After stopping the blowing, sampling and testing, slag discharge, and steel discharge are obtained:

[0074] The final molten steel [C] content is 0.63%, the final slag (∑FeO) content is 8.5%, and the molten steel oxygen activity is 88ppm.

[0075] The molten steel does not rephosphorize.

[0076] Comparative Example 1

[0077] 120t converter.

[0078] Smelting steel grade: X65.

[0079] After adding scrap steel and molten iron to the converter, normal blowing is carried out. The oxygen supply intensity of the top-blowing oxygen lance is 3.5m3 / (min·t steel), the oxygen supply intensity of the bottom-blowing oxygen lance is 0.05m3 / (min·t steel), and the position of the blowing oxygen lance is 1.4m. When the oxygen blowing progress of the top-blowing oxygen lance is 92%, the oxygen supply intensity of the top-blowing oxygen lance is reduced to 2.2m3 / (min·t steel), and the position of the oxygen lance is raised to 1.9m until the oxygen blowing is completed.

[0080] After stopping the blowing, sampling and testing, slag and steel tapping were carried out, and the following results were obtained:

[0081] The final slag (∑FeO) content is 23%, the final molten steel [C] content is 0.04%, and the molten steel oxygen activity is 952ppm.

[0082] Comparative Example 2

[0083] 120t converter.

[0084] Metallurgical steel type: 65# spring steel.

[0085] After adding scrap steel and molten iron to the converter, the normal blowing was carried out, the oxygen supply intensity was 4.m3 / (min·t steel), the bottom blowing gas supply intensity was 0.025m3 / (min·t steel), the blowing oxygen lance was at 1.4m, and when the oxygen blowing reached 95%, the lance was raised to 1.8m, and the bomb was dropped to measure the pouring time of 11min57s. When the blowing reached 11min57s (excluding the slag pouring time), the blowing was stopped and the lance was raised. After stopping the blowing, sampling and testing, slag discharge, and steel discharge were carried out, and the following results were obtained:

[0086] The final molten steel [C] content is 0.66%, the final slag (∑FeO) content is 11.5%, and the molten steel oxygen activity is 149ppm.

[0087] It can be seen from the above embodiments that, compared with the comparative example 1 of the conventional process, the process embodiments 1-4 of the present invention and the comparative example 1 all smelt low carbon steel grade X65, and the process parameters such as oxygen supply are basically the same. The (∑FeO) content in the final slag of the embodiments 1-3 using the technical solution of the present invention is reduced by 3-12%, and the oxygen activity of the molten steel is reduced by 147-590ppm; compared with the same high carbon steel grade 65# spring steel of the comparative example 2 of the conventional process, it can be seen that the high carbon steel grade 65# spring steel of the embodiment 5 using the technical solution of the present invention has basically the same oxygen supply parameters, the (∑FeO) content in the final slag is reduced by 3%, and the oxygen activity of the molten steel is reduced by 77ppm.

[0088] When a silicon-containing reducing agent is added, the molten steel will not rephosphorize even if the (∑FeO) content in the final slag drops below 15%.

[0089] Although the present invention has been described by referring to certain preferred embodiments of the present invention, it should be understood by those skilled in the art that the above is a further detailed description of the present invention in combination with specific embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. Based on the principle of the present invention, the technical adjustment schemes made by those skilled in the art in adjusting the timing of adding the reducing agent before stopping the blowing and lifting gun and making various changes in parameters and details such as the type of reducing agent and its addition amount should all fall within the scope of protection of the technical solution to be protected by the claims of the present invention.

Claims

1. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel [O], wherein blowing is performed according to the standard operation process of different steel grades, characterized in that: Before or at the same time as the gun is lifted to stop blowing at the end of blowing, reducing agent is added into the furnace from the high-level silo.

2. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claim 1, characterized in that: At the end of the first blowing, before or while the gun is lifted to stop blowing, reducing agent is added into the furnace from the high-level silo. If the molten steel is unqualified, re-blowing is performed. After the re-blowing, at the end of the second blowing, before or while the gun is lifted to stop blowing, reducing agent is added into the furnace from the high-level silo again.

3. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claim 1, characterized in that: Adding the reducing agent into the furnace from the high-level silo before or while the lance is being raised and blowing is being stopped means ensuring that the reducing agent added from the high-level silo falls into the molten pool before the oxygen lance is being raised or before the oxygen lance nozzle is exposed to the slag liquid surface.

4. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claim 1, characterized in that: The reducing agent is one or two of a carbon-containing reducing agent, a silicon-containing reducing agent, an aluminum-containing reducing agent, and a calcium-containing reducing agent.

5. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claims 1 and 4, characterized in that The carbon-containing reducing agent is one of coke particles, bituminous coal particles, anthracite particles, semi-coke particles, high-carbon coal gangue particles, and waste magnesium carbon brick particles.

6. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claims 1 and 4, characterized in that: The silicon-containing reducing agent is one of silicon mud balls, silicon carbide particles, ferrosilicon particles, and calcium silicon particles.

7. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claims 1 and 4, characterized in that: The aluminum-containing reducing agent is one of aluminum particles and aluminum ash balls.

8. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claims 1 and 4, characterized in that: The calcium-containing reducing agent is calcium carbide.

9. A method for reducing the oxidizability of steelmaking end slag and the oxygen activity of molten steel as claimed in claim 1, characterized in that: The reducing agent is added in an amount of 0.2-5 kg / t steel.