Method for reducing molten IF steel inclusions and improving cleanliness of molten steel

Abstract

The invention relates to a method for reducing molten IF steel inclusions and improving the cleanliness of molten steel. The method comprises the following technological processes of converter steelmaking, LF refining furnace, RH refining furnace and continuous casting. In the RH refining furnace process, cold steel nodules in a vacuum tank are eliminated during smelting, and metal manganese is added to compensate the mass content Mn to 0.07-0.15% according to the manganese content in chemical sample steel in the LF refining furnace process during circulation of molten steel in the vacuum tank; the method comprises the following steps: timely adjusting circulation argon to 60-80 Nm < 3 > / h, adjusting RH circulation argon flow to 90-120 Nm < 3 > / h and decarburizing for 18-25 minutes according to cold steel nodulation in a vacuum tank as well as oxygen content and vacuum degree in steel, performing oxygen determination operation after decarburization is finished, adjusting RH circulation argon flow to 70-90 Nm < 3 > / h, firstly adding carbon granules for deoxidation according to a fixed oxygen value, circulating for 2-3 minutes, performing secondary oxygen determination for aluminum-adding deoxidation alloying, and performing decarburization for 20-30 minutes. And the content of Als in the steel reaches the upper limit of the process target content, ferrotitanium and ferrocolumbium are added, and the process target is achieved by adjusting alloy component compensation at a time. The molten steel cleanliness and the yield are improved, and the smelting cost is reduced.

Description

Technical Field

[0001] The patented technology of the present invention relates to a steel smelting method, specifically to a method for reducing inclusions in IF steel molten steel and improving the cleanliness of molten steel. Background Art

[0002] With the improvement of environmental awareness and the restriction of energy consumption, the demand for low-carbon aluminum killed steel in the market has gradually increased. At present, low-carbon aluminum killed steel is more and more widely used in construction, automobiles, home appliances and other fields, and its market share is increasing year by year. With the development of the global low-carbon economy and the strengthening of environmental protection policies, the demand for low-carbon aluminum killed steel will continue to grow in the future. At the same time, with the advancement of technology and the expansion of application fields, the market demand space for low-carbon aluminum killed steel will be further expanded. With the continuous advancement of the production technology of low-carbon aluminum killed steel, the optimization and improvement of the process flow of blast furnace ironmaking, converter steelmaking, continuous casting and rolling have improved the output and quality of low-carbon aluminum killed steel. In addition, the research and development and application of new materials, such as high-strength steel and lightweight steel, provide new opportunities for the development of low-carbon aluminum killed steel.

[0003] In the smelting process, aluminum deoxidation alloying is used to refine the steel grains and improve the toughness of the steel. At the same time, the endogenous aluminum oxide (Al 2 O 3 ) inclusions, which have a high melting point and are solid in liquid steel, are easily gathered at the water outlet of the tundish during continuous casting, causing blockage and casting speed fluctuations. 2 O 3 It will be broken during the rolling process and distributed continuously along the rolling direction, causing serious defects. Summary of the invention

[0004] The purpose of the present invention is to accurately control the smelting process and the appropriate smelting temperature and time in the smelting process, and to accurately control the content of C, Si, Al and Mn elements in the steel in terms of composition control, so as to ensure the purity and uniformity of the molten steel to ensure the mechanical properties and welding properties of the steel.

[0005] The technical solution of the present invention is:

[0006] A method for reducing inclusions in IF steel molten steel and improving the cleanliness of molten steel, comprising the following process flow: converter steelmaking - LF refining furnace - RH refining furnace - continuous casting;

[0007] RH refining furnace process: eliminate cold steel nodules in the vacuum tank during smelting, and start circulating the molten steel in the vacuum tank. Add metallic manganese to compensate the manganese content in the chemical sample steel of the LF refining furnace process to a mass content of Mn: 0.07-0.15%; adjust the circulating argon gas 60-80Nm in time according to the cold steel nodules in the vacuum tank, the oxygen content in the steel, and the vacuum degree. 3 / h, to avoid the violent carbon-oxygen reaction, which may cause the splashing slag steel to stick to the camera, and the accumulation of slag in the hot bend pipe to affect the exhaust function and decarburization effect. The carbon-oxygen reaction tends to be stable, and the RH circulation argon flow rate is adjusted to 90-120Nm 3 / h, decarburization for 18-25min, after decarburization, carry out oxygen determination operation, adjust the RH circulation argon flow rate to 70-90Nm 3 / h, according to the oxygen value, carbon particles are first added for deoxidation, and the cycle is 2 to 3 minutes. Secondary oxygen determination is carried out to add aluminum for deoxidation and alloying, so that the Als content in the steel reaches the upper limit of the process target content, and titanium iron and niobium iron are added to adjust the alloy composition compensation at one time to achieve the process target.

[0008] Preferably, the converter steelmaking process: in the early stage of converter smelting, the amount of lime is determined according to the type of steel and the semi-steel [P] content for slag making and dephosphorization. When the mass content of semi-steel [P] is less than 0.15%, the amount of lime is taken as the lower limit; when the mass content of semi-steel [P] is greater than 0.15%, the amount of lime is taken as the upper limit. The range of added lime is 20 to 30 kg / t.

[0009] Preferably, the converter steelmaking process is controlled as follows: the S mass content of the semi-steel entering the furnace is ≤0.003%, the converter end temperature is 1670-1680°C, the continuous pulling temperature is 1660-1670°C, the process smelting oxygen lance position is controlled at 1.4-1.7 meters, the slag lance position is controlled at 1.5-1.8 meters, the oxygen pressure is controlled at 0.7-0.9Mpa, and the oxygen flow rate is 24000-36000Nm 3 / h, within 2 to 3 minutes of blowing, the oxygen flow rate is 24000Nm 3 / h; according to the flame state and the sound in the furnace, the slagging situation and blowing state are determined, the gun position and cold material are adjusted in time to smoothly control the blowing, and the oxygen supply time is controlled at 11-15min. After the blowing is completed, TSO is used to measure the oxygen content of 700-900ppm and the carbon content C: 0.03-0.04%, so as to meet the requirements of the steel grade and organize the steelmaking.

[0010] Preferably, after the steel grade requirements are met and the steel is tapped, 200-300 kg of refined slag is added per furnace, and the optimal control mass content at the end point is P≤0.010%, S≤0.005%, and the oxygen content of the argon station is 600-800 ppm. The purpose of RH natural decarburization is achieved, the frequency of oxygen lance use is reduced, the oxygen lance oxygen blowing reduces the overoxidation of slag and molten steel, and the service life of the oxygen lance is increased;

[0011] The refined slag includes the following raw materials by mass content: Ca0: 18-25%, AL 2 0 3: 5~8%、Si0 2: 6~10%、CaF 2: ≥15%、CaC 4:7~10%, AL: 2~5% P≤0.08%, S≤0.018%.

[0012] Preferably, the LF refining furnace process: the argon gas flow rate is set to ≤1500NL / min, the feeding time is controlled to 2-3min, 100-200kg / furnace of refined slag and 150-300kg / furnace of aluminum ladle slag modifier are added; the amount of lime added before the first heating is 600-800kg / furnace, and the feeding is fully stirred and melted after the feeding is completed, and the heating treatment is carried out. The electrode heating adopts a long arc in the early stage, and the six-speed voltage is heated for 2-3min to slag, and the short arc + foam slag operation is adopted in the later stage, and the four-speed voltage is heated. After the first heating is completed, the argon gas is adjusted to 300-500NL / min for 3-5min to uniform temperature and composition operation, and the argon gas is adjusted to 150-300NL / min for temperature measurement. According to the measured temperature, whether the secondary heating and compensation temperature are carried out to the first furnace temperature of 1650-1660°C and the continuous furnace temperature of 1610-1620°C, the chemical sample composition compensation is carried out;

[0013] Aluminum ladle slag modifier includes the following raw materials by mass content: AL: 50-55%, AL 2 0 3: 15~20%, Ca0: 5~15%, MgO<5%, Si0 2 <3%, P<0.14%, S<0.2%.

[0014] Preferably, after smelting in the LF refining furnace, the chemical composition of the samples meets the quality requirements, C: ≤0.04, Si: ≤0.01%, Mn: 0.07-0.15%, P ≤0.010%, S ≤0.008%.

[0015] Preferably, the RH refining furnace process: top gun baking operation is carried out before smelting treatment, the vacuum tank immersion pipe and 12 circulation pipes are ventilated, the cold steel is prohibited from blocking and affecting the circulation of molten steel, the coal-oxygen flow ratio is adjusted to 1:1, the gun position is 4.0-5.5m, and the flow rate is 150-180Nm 3 / h, making the inner wall temperature of the tank greater than 1400℃.

[0016] Preferably, the mass content of each component in the RH refining furnace process target is:

[0017] C≤0.0030%, Si≤0.02%, Mn:0.07~0.15%, P≤0.012%, S≤0.008%, Nb:0.010~0.020, Ti:0.020~0.035%, Cu≤0. 05. Cr≤0.05, Ni≤0.05, Mo≤0.020, V≤0.004, Cu+Cr+Ni≤0.07, B≤0.0005, ALs: 0.025~0.055%, [N]≤0.0030.

[0018] Preferably, after the RH refining furnace process completes the process target, the vacuum degree is maintained at ≤67Pa, the cyclic degassing is 18 to 25 minutes, the pure degassing time is ≥8 minutes, and the process is allowed to stand for 15 to 20 minutes; the RH first furnace tapping temperature is: 1615 to 1625°C, and the continuous pulling temperature is: 1580 to 1590°C.

[0019] Preferably, the IF steel molten steel smelting range includes the following components in mass percentage: C≤0.0030%, Si≤0.02%, Mn:0.07-0.15%, P≤0.012%, S≤0.008%, Nb:0.010-0.020, Ti:0.020-0.035%, Cu≤0.05, Cr≤0.05, Ni≤0.05, Mo≤0.020, V≤0.004, Cu+Cr+Ni≤0.07, B≤0.0005, ALs:0.025-0.055%, [N]≤0.0030, and the balance is iron and its inevitable impurities.

[0020] The beneficial effects of the present invention are:

[0021] A method for reducing inclusions in IF steel (low carbon steel) molten steel and improving the cleanliness of molten steel, wherein after complete decarburization in an RH vacuum furnace, part of carbon particles are preferentially added for deoxidation according to the oxygen content in the steel of an oxygen meter. Carbon is the best deoxidizer under vacuum conditions. Carbon particles are added to remove part of the free oxygen in the molten steel to replace aluminum deoxidation by utilizing the carbon-oxygen reaction, thereby reducing the internal inclusions Al generated by aluminum deoxidation. 2 O 3 content, improve the cleanliness of molten steel, and increase the yield rate. Deoxidation of particles can reduce the amount of aluminum added, reduce smelting costs, and increase added value. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific embodiments.

[0023] Examples 1-6

[0024] A method for vanadium extraction and semi-steel smelting non-oriented silicon steel, comprising converter vanadium extraction, converter desulfurization, converter steelmaking, LF refining, RH refining, and continuous casting processes; the specific control parameters are as follows:

[0025] (1) Converter steelmaking process: The amount of lime is determined according to the type of steel and the content of semi-steel [P]. When the mass content of semi-steel [P] is less than 0.15%, the amount of lime is taken as the lower limit. When the mass content of semi-steel [P] is greater than 0.15%, the amount of lime is taken as the upper limit. The range of lime addition is 20 to 30 kg / t.

[0026] Converter steelmaking process control: S mass content of semi-steel entering the furnace ≤ 0.003%, converter end temperature 1670 ~ 1680 ℃, continuous pulling temperature 1660 ~ 1670 ℃, process smelting oxygen lance position controlled at 1.4 ~ 1.7 meters, slag lance position controlled at 1.5 ~ 1.8 meters, oxygen pressure controlled at 0.7 ~ 0.9Mpa, oxygen flow 24000 ~ 36000Nm 3 / h, within 2 to 3 minutes of blowing, the oxygen flow rate is 24000Nm 3 / h; according to the flame state and the sound in the furnace, the slagging situation and blowing state are determined, the gun position and cold material are adjusted in time to smoothly control the blowing, and the oxygen supply time is controlled at 11-15min. After the blowing is completed, TSO is used to measure the oxygen content of 700-900ppm and the carbon content C: 0.03-0.04%, so as to meet the requirements of the steel grade and organize the steelmaking.

[0027] After steel tapping is completed, add 200-300kg of refined slag per furnace, and the optimal control quality content at the end point is P≤0.010%, S≤0.005%, and the oxygen content of the argon station is 600-800ppm. The purpose of RH natural decarburization is achieved, the frequency of oxygen lance use is reduced, the oxygen lance blowing oxygen to slag and molten steel is reduced, and the service life of the oxygen lance is increased.

[0028] The refined slag includes the following raw materials by mass content: Ca0: 18-25%, AL 2 0 3: 5~8%、Si0 2: 6~10%、CaF 2: ≥15%、CaC 4: 7~10%, AL: 2~5% P≤0.08%, S≤0.018%.

[0029] The control parameters of the converter steelmaking process of Examples 1-6 are shown in Table 1.

[0030] Table 1 Control parameters of converter steelmaking process in Example 1-6

[0031]

[0032]

[0033] (2) LF refining process: argon gas flow rate is set to ≤1500NL / min, the feeding time is controlled to 2-3min, 100-200kg / furnace of refined slag and 150-300kg / furnace of aluminum ladle modifier are added; the amount of lime added before the first heating is 600-800kg / furnace, and the feeding is fully stirred and melted after the feeding is completed, and then heating treatment is carried out. In the early stage of electrode heating, long arc is used, and six-speed voltage is used to heat the slag for 2-3min. In the later stage, short arc + foam slag operation is used, and four-speed voltage is used for heating. After the first heating is completed, the argon gas is adjusted to 300-500NL / min for 3-5min to uniform temperature and composition operation, and the argon gas is adjusted to 150-300NL / min for temperature measurement. According to the measured temperature, whether to perform secondary heating and compensation temperature is 1650-1660℃ for the first furnace and 1610-1620℃ for the continuous furnace, and chemical sample composition compensation is carried out. After smelting in the LF refining furnace, the chemical composition of the samples met the quality requirements, C: ≤0.04, Si: ≤0.01%, Mn: 0.07~0.15%, P ≤0.010%, S ≤0.008%.

[0034] Aluminum ladle slag modifier includes the following raw materials by mass content: AL: 50-55%, AL 2 0 3: 15~20%, Ca0: 5~15%, MgO<5%, Si0 2 <3%, P<0.14%, S<0.2%.

[0035] The control parameters of the LF refining process of Examples 1-6 are shown in Table 2.

[0036] Table 2 LF refining process control parameters

[0037]

[0038]

[0039] (3) RH refining furnace process: The top gun baking operation is carried out before the continuous smelting process of the RH process. The 12 circulation pipes of the vacuum tank immersion pipe are well ventilated. The cold steel is prohibited from clogging and affecting the circulation of the molten steel. The coal-oxygen ratio is adjusted to 1:1. The gun position is 4.0-5.5m, and the flow rate is 150-180Nm 3 / h, so that the tank temperature (tank inner wall temperature) is greater than 1400℃. Eliminate the cold steel nodules in the vacuum tank, and start the circulation of the molten steel in the vacuum tank. According to the manganese content in the chemical sample steel of the previous process (LF furnace), add metallic manganese to compensate to Mn: 0.07~0.15%. According to the cold steel nodules in the vacuum tank, the oxygen content in the steel, and the vacuum degree, timely adjust the circulating argon gas to 60~80Nm3 / h to avoid intense carbon-oxygen reaction. The splashing slag steel will stick to the camera, and the accumulation of steel slag in the hot bend pipe will affect the exhaust function and decarburization effect. The carbon-oxygen reaction tends to be stable, and the RH circulating argon gas flow rate is adjusted to 90~120Nm3 / h. Decarburization takes 18 to 25 minutes. After decarburization, oxygen determination is performed and the circulating argon gas is adjusted to 70 to 90 Nm 3 / h According to the oxygen value, carbon particles are added first for deoxidation, and the cycle is 2 to 3 minutes, and the secondary oxygen is determined to add aluminum for deoxidation and alloying. The Als content in the steel reaches the upper limit of the process target content. Add titanium iron and niobium iron, and adjust the alloy composition compensation at one time to achieve the process target, C≤0.0030%, Si≤0.02%, Mn:0.07~0.15%, P≤0.012%, S≤0.008%, Nb:0.010~0.020%, Ti:0.020~0.035%, Cu≤0.05%, Cr≤0.05%, Ni≤0.05%, Mo≤0.020%, V≤0.004%, Cu+Cr+Ni≤0.07%, B≤0.0005%, ALs: 0.025~0.055%. [N]≤0.0030%, maintain vacuum degree≤67Pa, cycle degassing for 18-25min, pure degassing time≥8min, stand for 15-20min. RH first furnace tapping temperature: 1615-1625℃, continuous other furnace temperatures: 1580-1590℃.

[0040] The control parameters of the RH refining process of Examples 1-6 are shown in Tables 3 and 4.

[0041] Table 3 Control parameters of RH refining process in Example 1-6

[0042]

[0043]

[0044] Table 4 Control parameters of RH refining process of Example 1-6 continued

[0045]

[0046] (4) Continuous casting process: achieving continuous casting at a constant speed.

[0047] The main chemical components and mass percentages of the molten steel obtained in Examples 1-6 are shown in Tables 5 and 6.

[0048] Table 5 Chemical composition and mass percentage of molten steel in Examples 1-6 (%)

[0049] Example C Si Mn P S Als N / ppm O / ppm 1 0.0011 0.01 0.07 0.009 0.005 0.025 20 5 2 0.0012 0.01 0.09 0.010 0.004 0.038 12 3 3 0.0013 0.01 0.10 0.009 0.005 0.030 18 6 4 0.0010 0.02 0.11 0.008 0.006 0.042 19 5 5 0.0018 0.01 0.13 0.010 0.004 0.040 13 8 6 0.0020 0.02 0.15 0.008 0.003 0.055 20 10

[0050] Table 6 Chemical composition and mass percentage of molten steel in Example 1-6 (%)

[0051]

[0052] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for reducing inclusions in molten steel of IF steel and improving the cleanliness of molten steel, characterized in that: It includes the following process flow: converter steelmaking - LF refining furnace - RH refining furnace - continuous casting; RH refining furnace process: eliminate cold steel nodules in the vacuum tank during smelting, and start circulating the molten steel in the vacuum tank. Add metallic manganese to compensate the manganese content in the chemical sample steel of the LF refining furnace process to a mass content of Mn: 0.07-0.15%; adjust the circulating argon gas 60-80Nm in time according to the cold steel nodules in the vacuum tank, the oxygen content in the steel, and the vacuum degree. 3 / h, the carbon-oxygen reaction is stable, adjust the RH cycle argon flow rate to 90~120Nm 3 / h, decarburization for 18-25min, after decarburization, carry out oxygen determination operation, adjust the RH circulation argon flow rate to 70-90Nm 3 / h, according to the oxygen value, carbon particles are first added for deoxidation, and the cycle is 2 to 3 minutes. Secondary oxygen determination is carried out to add aluminum for deoxidation and alloying, so that the Als content in the steel reaches the upper limit of the process target content, and titanium iron and niobium iron are added to adjust the alloy composition compensation at one time to achieve the process target.

2. A method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 1, characterized in that: In the early stage of converter smelting, the amount of lime is determined according to the type of steel and the semi-steel [P] content for slag making and dephosphorization. When the mass content of semi-steel [P] is less than 0.15%, the amount of lime is taken as the lower limit; when the mass content of semi-steel [P] is greater than 0.15%, the amount of lime is taken as the upper limit. The range of lime addition is 20 to 30 kg / t.

3. The method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 1, characterized in that: Converter steelmaking process control: S mass content of semi-steel entering the furnace ≤ 0.003%, converter end temperature 1670 ~ 1680 ℃, continuous pulling temperature 1660 ~ 1670 ℃, process smelting oxygen lance position controlled at 1.4 ~ 1.7 meters, slag lance position controlled at 1.5 ~ 1.8 meters, oxygen pressure controlled at 0.7 ~ 0.9Mpa, oxygen flow 24000 ~ 36000Nm 3 / h, within 2 to 3 minutes of blowing, the oxygen flow rate is 24000Nm 3 / h; according to the flame state and the sound in the furnace, the slagging situation and blowing state are determined, the gun position and cold material are adjusted in time to smoothly control the blowing, and the oxygen supply time is controlled at 11-15min. After the blowing is completed, TSO is used to measure the oxygen content of 700-900ppm and the carbon content C: 0.03-0.04%, so as to meet the requirements of the steel grade and organize the steelmaking.

4. The method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 1, characterized in that: After steel tapping is completed, add 200-300 kg of refined slag per furnace to meet the requirements of steel grade. The optimal control quality content at the end point is P: ≤0.010%, S: ≤0.005%, and oxygen content at the argon station: 600-800 ppm; The refined slag includes the following raw materials by mass content: Ca0: 18-25%, Al20 3: 5~8%、Si0 2: 6~10%、CaF 2: ≥15%、CaC 4: 7~10%, AL: 2~5% P≤0.08%, S≤0.018%.

5. The method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 1, characterized in that: LF refining furnace process: argon gas set flow rate ≤ 1500NL / min, charging time controlled 2-3min, add 100-200kg / furnace of refined slag, 150-300kg / furnace of aluminum ladle slag modifier; lime addition amount before primary heating is 600-800kg / furnace, fully stir and melt after charging, and heat treatment, long arc is used for electrode heating in the early stage, six-speed voltage is used for slag heating for 2-3min, short arc + foam slag operation is used in the later stage, four-speed voltage is used for heating, after primary heating is completed, argon gas is adjusted to 300-500NL / min for 3-5min for uniform temperature and composition operation, argon gas is adjusted to 150-300NL / min for temperature measurement, and secondary heating and compensation temperature are carried out according to the measured temperature to the first furnace temperature of 1650-1660℃, and the continuous furnace temperature is 1610-1620℃, and chemical sample composition compensation is carried out; The aluminum ladle slag modifier includes the following raw materials by mass content: AL: 50-55%, AL203: 15-20%, Ca0: 5-15%, MgO<5%, Si02<3%, P<0.14%, S<0.2%.

6. A method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 5, characterized in that: After smelting in the LF refining furnace, the chemical composition of the samples met the quality requirements, C≤0.04, Si≤0.01%, Mn: 0.07~0.15%, P≤0.010%, S≤0.008%.

7. The method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 1, characterized in that: The top gun baking operation is carried out before the smelting treatment in the RH refining furnace process. The 12 circulation pipes of the vacuum tank immersion pipe are ventilated. The cold steel is prohibited from blocking and affecting the circulation of the molten steel. The coal-oxygen flow ratio is adjusted to 1:1, the gun position is 4.0-5.5m, and the flow rate is 150-180Nm 3 / h, making the inner wall temperature of the tank greater than 1400℃.

8. A method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 7, characterized in that: The mass content of each component in the RH refining furnace process target: C≤0.0030%, Si≤0.02%, Mn:0.07~0.15%, P≤0.012%, S≤0.008%, Nb: 0.010~0.020, Ti: 0.020~0.035%, Cu≤0.05, Cr≤0.05, Ni≤0.05, Mo≤0.020, V≤0.004, Cu+Cr+Ni≤0.07, B≤0.0005, ALs: 0.025~0.055%, [N]≤0.0030.

9. The method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 1, characterized in that: After the RH refining furnace process completes the process target, the vacuum degree is maintained at ≤67Pa, the cycle degassing is 18-25min, the pure degassing time is ≥8min, and the process is left to stand for 15-20min; RH first furnace tapping temperature: 1615~1625℃, continuous pulling temperature: 1580~1590℃.

10. The method for reducing inclusions in molten IF steel and improving the cleanliness of molten steel according to claim 1, characterized in that: The IF steel smelting range includes the following components in mass percentage: C≤0.0030%, Si≤0.02%, Mn:0.07~0.15%, P≤0.012%, S≤0.008%, Nb:0.010~0.020, Ti:0.020~0.035%, Cu≤0.05, Cr≤0.05, Ni≤0.05, Mo≤0.020, V≤0.004, Cu+Cr+Ni≤0.07, B≤0.0005, ALs:0.025~0.055%, [N]≤0.0030, the balance is iron and its inevitable impurities.

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