Molten steel total oxygen control method

Abstract

The invention discloses a molten steel total oxygen control method, which comprises the procedures of molten iron pretreatment desulfurization, converter treatment, LF (ladle furnace) refining and continuous casting, and the specific control parameters are as follows: in the converter procedure, a carbon-aluminum composite deoxidation process is applied in the tapping process, and the free oxygen at the end point of a converter is less than or equal to 600ppm; an LF refining procedure: adopting a carbon-aluminum composite deoxidation slag forming process; and a continuous casting process: a continuous casting tundish adopts stable liquid level casting, the nitrogen increase of molten steel is less than or equal to 0.0005%, and the total oxygen content of the molten steel is less than or equal to 0.0025%. On the premise of meeting the requirement of steel for the welded gas cylinder, the using amount of aluminum is reduced, and effective control over total oxygen of molten steel is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a method for controlling the total oxygen in molten steel. Background Art

[0002] Since the 2050 production line of HBIS Tangsteel was put into production, it has continuously conducted in-depth market research, seized market opportunities, and actively promoted high-quality steel to customers. At present, Tangsteel has established direct contacts with 60% of domestic production enterprises of steel for welded gas cylinders, and has provided samples for trial use to 7 domestic top-ten customers respectively. The product quality has been widely recognized, and the product has gradually moved from trial use to mass production. The hot-rolled steel plate for welded gas cylinders is a high-value-added product developed by the 2050 line to meet market demands. This product is mainly used to manufacture liquefied petroleum gas cylinders, acetylene cylinders, etc., with a working pressure above 16 kg / cm 2 above, and has broad market prospects.

[0003] Since the manufacturing process of liquefied petroleum gas cylinders is relatively complex and has high requirements for performance during stamping forming, such as small differences in transverse and longitudinal properties of the steel plate, and its welding performance requires the steel plate to have a low carbon equivalent. The production of welded gas cylinders mainly consists of two processes: drawing and welding. During processing, phenomena such as necking breakage and punching cracks often occur, and the quality of the finished product is directly related to the life and property safety of users. Therefore, strict requirements are imposed on the various properties of the hot-rolled steel coil (plate) for manufacturing such cylinders. In addition to considering ensuring the molten steel composition, it is also necessary to consider the control of the total oxygen content in the molten steel and the inclusion control level. The non-metallic inclusions in the hot-rolled steel strip should comply with the following table

[0004] In order to reduce production costs and increase enterprise benefits, HBIS Tangsteel adopts a single-link process flow of KR-BOF-LF-CC for the hot-rolled steel plate for welded gas cylinders. The production difficulty is high. Using the normal aluminum-based deoxidation process, it is mainly reflected in the unstable control of inclusions. There are often cases where type A inclusions exceed grade 2.0, and the proportion of the total oxygen in the tundish above 0.0030% is 55%, resulting in downgrading of the plate coil and causing cost waste to the company. Therefore, it is imperative to explore a new smelting process. Summary of the Invention

[0005] The purpose of the present invention is to propose a method for controlling the total oxygen in molten steel. By means of hot metal pretreatment desulfurization, selection of the converter slag blocking method, application of a carbon-aluminum composite deoxidation process during tapping, coordination of LF refining power supply and bottom argon blowing in the ladle, adoption of a carbon-aluminum composite deoxidation slag formation process, coordination of alloy addition and bottom argon blowing in the ladle during LF refining, principle of molten steel deoxidation during LF refining, and control of the static blowing time during LF refining, on the premise of meeting the requirements of steel for welded gas cylinders, the amount of aluminum used is reduced, and the total oxygen content in the molten steel is controlled ≤ 0.0025%.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: A method for controlling the total oxygen content of molten steel, the control method includes: hot metal pretreatment desulfurization, converter, LF refining, continuous casting process, and the specific control parameters are as follows: (1) Converter process: During the tapping process, a carbon-aluminum composite deoxidation process is applied. When 5-15% of the steel is tapped, 0.5-3 kg / t of coal-based carburizer is added to the ladle for pre-deoxidation; when 15-30% of the steel is tapped, 1.5-3 kg / t of ferrosilicon aluminum is added to the ladle for deoxidation until the acid-soluble aluminum content in the molten steel reaches 0.0200-0.0400%; when the tapping reaches 90-95%, the flow rate of bottom blowing argon in the ladle is adjusted to 20-100 NL / min until the tapping is completed, and the free oxygen at the converter end point is ≤0.0600%; (2) LF refining process: Before power supply, the steel slag in the ladle is crusty, and the Ar blowing control range is: 600-1000 NL / min for breaking the crust; for the ladle without remaining slag from casting, when starting to heat, the slag layer is relatively thin, and low or medium-low voltage is used, and the power supply time is 2-5 minutes; for the ladle with remaining slag from casting, high voltage is directly applied for heating up; the deoxidized aluminum for molten steel is added to the ladle as early as possible, and the number of aluminum supplementing times is ≤2 times; (2) LF refining process: Before power supply, the steel slag in the ladle is crusty, and the Ar blowing control range is: 600-1000 NL / min for breaking the crust; for the ladle without remaining slag from casting, when starting to heat, the slag layer is relatively thin, and low or medium-low voltage is used, and the power supply time is 2-5 minutes; after the slag is basically formed, some slag materials can be appropriately added to ensure the submerged arc effect and increase the voltage level; the final refining slag only needs to meet the slag-making requirements for aluminum-containing steel; during the alloy addition period, the Ar blowing control range is: 400-800 NL / min, and the exposed diameter of the molten steel is 400-500 mm, with the slag surface fluctuating without splashing as the standard, and stirring for 3-4 minutes to make the inclusions float up sufficiently; for the ladle with remaining slag from casting, high voltage is directly applied for heating up; the deoxidized aluminum for molten steel is added to the ladle as early as possible, and the number of aluminum supplementing times is ≤2 times; (3) Continuous casting process: The continuous casting tundish adopts stable liquid level casting, the nitrogen increase in the molten steel is ≤0.0005%, and the total oxygen content of the molten steel is ≤0.0025%.

[0007] In the converter process of the present invention, the slag falling amount is ≤2.5 kg / t steel; the coal-based carburizer is carbon powder, and the mass percentage of C≥92%.

[0008] In the converter process of the present invention: The slag blocking method of the converter adopts front slag blocking plus a slag blocking plug, and the rear slag blocking adopts a slide plate for slag blocking; the number of reblowing times is ≤1 time.

[0009] The LF refining process described in the present invention: The LF refining uses a carbon-aluminum composite deoxidation and slag formation process; 0.05 - 0.15 kg / t of molten steel of coal-based carbon increasing agent is added for deoxidation and slag formation operation in the first 3 minutes during the power supply process, and then aluminum-making slag agent is added for white slag formation operation. After the white slag is formed, to ensure the white slag time, during the power supply process, 0.025 - 0.05 kg / t of molten steel of coal-based carbon increasing agent is added, and the interval between each addition is 1 - 4 minutes.

[0010] The LF refining process described in the present invention: For the LF refining, the shell breaking, slag-making material adding, desulfurization, carbon increasing, slag washing, and deoxidation at the station use a strong blowing mode.

[0011] The LF refining process described in the present invention: During the LF refining for homogenizing the composition, temperature, feeding aluminum wire / carbon wire, and adding alloys, the blowing Ar control range is 400 - 800 NL / min, and the exposed diameter of the molten steel is 400 - 500 mm. Based on the fluctuation of the slag surface without splashing, stirring is carried out for 3 - 4 minutes to make the inclusions float up sufficiently.

[0012] The LF refining process described in the present invention: During the LF refining for temperature measurement, sampling, oxygen determination, power supply, feeding titanium wire, calcium treatment, etc., the blowing Ar control range is 100 - 400 NL / min, and the exposed diameter of the molten steel is 10 - 20 mm, adopting a static blowing mode.

[0013] The LF refining process described in the present invention: From the end of calcium treatment to tapping in the LF refining, the blowing Ar control range is 20 - 100 NL / min.

[0014] The continuous casting process described in the present invention: During the normal steel casting process, the molten steel amount in the tundish is not less than 85% of the total molten steel amount when the tundish is full. When changing the tundish for continuous casting heats, the minimum molten steel amount in the tundish is not less than 65% of the total molten steel amount when the tundish is full, meeting the requirement of stable liquid surface casting with a full tundish.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The slag blocking method of the converter in the present invention adopts front slag blocking plus a slag stopper, and the rear slag blocking adopts a slide plate for slag blocking, which can effectively reduce the slag volume under the converter, with the reblow ≤ 1 time, making the free oxygen at the end of the converter ≤ 0.0600%. During the tapping process of the converter, the carbon-aluminum composite deoxidation process is applied, which can effectively reduce the dosage of aluminum deoxidizer, reduce the content of Al2O3 in the molten steel, and reduce the generation of total oxygen in the molten steel; while controlling the burning loss of Als in the molten steel, it also reduces the waste of alloy cost; 2. The cooperation between the power supply during LF refining in the present invention and the bottom argon blowing of the ladle reduces the erosion rate of the ladle refractories and reduces the generation of total oxygen in the molten steel; 3. The present invention adopts a carbon-aluminum composite deoxidation slag formation process during LF refining to minimize the total amount of endogenous molten steel oxygen; 4. The cooperation between the alloy addition during LF refining in the present invention and the bottom argon blowing of the ladle enables the maximum removal of the total oxygen of the incoming molten steel; 5. The deoxidation aluminum during LF refining of the present invention is added to the ladle as early as possible, with the aluminum supplement times ≤ 2 times, making the deoxidation products generate in the form of large particle inclusions as much as possible, which is beneficial to removal and gives sufficient floating time; 6. The continuous casting in the present invention adopts a stable liquid surface casting, reducing the contact between the molten steel and air and reducing the slag entrainment during the casting process. Specific Embodiments

[0016] The present invention will be further described in detail below in conjunction with specific embodiments. Embodiment 1

[0017] In this embodiment, HP295 is smelted using the above control method, and the ladle volume is 200t. The specific implementation plan is as follows: (1) Converter process: The slag blocking method of the converter adopts front slag blocking plus a slag stopper, and the rear slag blocking adopts a slide plate for slag blocking. The slag volume under the converter is 2.1 kg / t steel, and the reblow is 1 time; during the tapping process, the carbon-aluminum composite deoxidation process is applied. When 5% of the steel is tapped, 0.20 kg / t of coal-based carbon powder as a carbon increasing agent is added to the ladle for preliminary deoxidation; when 15% of the steel is tapped, 1.5 kg / t of ferrosilicon aluminum is added to the ladle for deoxidation until the acid-soluble aluminum content in the molten steel reaches 0.0202%; when 90% of the steel is tapped, the bottom argon blowing flow rate of the ladle is adjusted to 50 NL / min until the tapping is completed, and the free oxygen at the end of the converter is 0.0526%; (2) LF refining process: During LF refining, the ladle is broken, slag forming materials are added, desulfurization, carbon increasing, slag washing, and deoxidation are carried out in a strong blowing mode.

[0018] Before power supply, there is a slag crust in the ladle. The Ar blowing control range for breaking the crust is 600 NL / min. For the ladle without remaining slag after casting, when starting heating, the slag layer is relatively thin. Use low or medium-low voltage, and the power-on time is 2 minutes. After the slag is basically formed, some slag materials can be appropriately added to ensure the submerged arc effect and increase the voltage level. The final slag in refining only needs to meet the slag-making requirements for aluminum-containing steel. During alloy addition, the Ar blowing control range is 400 NL / min, and the exposed diameter of the molten steel is 400 mm. Based on the fluctuation of the slag surface without splashing, stir for 3 minutes to make the inclusions float up sufficiently. For the ladle with remaining slag after casting, directly supply power and increase the temperature using high voltage. Add deoxidizing aluminum to the ladle as early as possible, and the number of aluminum supplement times is 1 time.

[0019] The LF refining adopts the process of carbon-aluminum composite deoxidation and slag formation. During the first 3 minutes of the power supply process, add 0.05 kg / t of molten steel of coal-based carburant for deoxidation and slag-making operation. Then add aluminum slag-making agent for making white slag operation. After the white slag is formed, to ensure the white slag time, during the power supply process, add 0.025 kg / t of molten steel of coal-based carburant, and the interval between each addition is 1 minute.

[0020] During LF refining for uniform composition, temperature, feeding aluminum wire / carbon wire, and alloy addition, the Ar blowing control range is 400 NL / min, and the exposed diameter of the molten steel is 400 mm. Based on the fluctuation of the slag surface without splashing, stir for 3 minutes to make the inclusions float up sufficiently.

[0021] During LF refining for temperature measurement, sampling, oxygen determination, power supply, feeding titanium wire, calcium treatment, etc., the Ar blowing control range is 100 NL / min, and the exposed diameter of the molten steel is 10 mm. The static blowing mode is adopted.

[0022] From the end of calcium treatment to tapping in LF refining, the Ar blowing control range is 20 NL / min.

[0023] (3) Continuous casting process: The continuous casting tundish adopts stable liquid level casting. The nitrogen increase in the molten steel is 3 ppm, and the total oxygen content in the molten steel is 23 ppm. During the normal continuous casting process, the amount of molten steel in the tundish is 90.1% of the total molten steel amount when the tundish is full. When changing the ladle during continuous casting, the amount of molten steel in the tundish is 67.6% of the total molten steel amount when the tundish is full. Example 2

[0024] In this example, HP295 is smelted using the above control method, and the ladle volume is 200 t. The specific implementation plan is as follows: (1)Converter process: The slag blocking method in the converter adopts front slag blocking plus a slag stopper, and the back slag blocking adopts a slide plate for slag blocking. The amount of slag flowing into the ladle is 1.8 kg / t of steel, and there is no re-blowing; during the tapping process, a carbon-aluminum composite deoxidation process is applied. When 5% of the steel is tapped, 5 kg of coal-based recarburizer carbon powder is added per 100 tons of steel for pre-deoxidation; when 15% of the steel is tapped, 150 kg of ferrosilicon aluminum is added per 100 tons of steel for deoxidation until the acid-soluble aluminum content in the molten steel reaches 0.0206%; when 90% of the steel is tapped, the flow rate of bottom blowing argon in the ladle is adjusted to 20 NL / min. By the end of tapping, the free oxygen at the converter end point is 0.0498%.

[0025] (2)LF refining process: For the LF refining process, when entering the station, breaking the slag crust, adding slag-making materials, desulfurizing, recarburizing, slag washing, and deoxidizing adopt a strong blowing mode.

[0026] Before power supply, there is a slag crust in the ladle. The control range of blowing Ar for slag crust breaking is 600 NL / min; for the furnace without remaining slag from casting, when starting heating, the slag layer is relatively thin, and low or medium-low voltage is used, and the power-on time is 2 minutes; after the slag is basically formed, some slag-making materials can be appropriately added to ensure the submerged arc effect and increase the voltage level; the final slag in refining only needs to meet the slag-making requirements for aluminum-containing steel; during the addition of alloys, the control range of blowing Ar is 400 NL / min, and the exposed diameter of the molten steel is 400 mm. Based on the fluctuation of the slag surface without splashing, stir for 3 minutes to make the inclusions float up sufficiently; for the furnace with remaining slag from casting, directly supply power and raise the temperature using high voltage; the deoxidizing aluminum for the molten steel should be added to the ladle as early as possible, and the number of aluminum additions is 1 time.

[0027] The LF refining adopts a carbon-aluminum composite deoxidation and slag formation process; 0.05 kg / t of steel of coal-based recarburizer is added for deoxidation and slag formation operations in the first 3 minutes during the power supply process, and then aluminum-based slag-making agent is added for making white slag. After the white slag is formed, to ensure the white slag time, 0.025 kg / t of steel of coal-based recarburizer is added during the power supply process, with an interval of 1 minute for each addition.

[0028] During the LF refining for homogenizing composition, temperature, feeding aluminum wire / carbon wire, and adding alloys, the control range of blowing Ar is 400 NL / min, and the exposed diameter of the molten steel is 400 mm. Based on the fluctuation of the slag surface without splashing, stir for 3 minutes to make the inclusions float up sufficiently.

[0029] For temperature measurement, sampling, oxygen determination, power supply, feeding titanium wire, calcium treatment, etc. in LF refining, the control range of blowing Ar is 100 NL / min, and the exposed diameter of the molten steel is 10 mm, adopting a static blowing mode.

[0030] From the end of calcium treatment to tapping out in LF refining, the control range of blowing Ar is 20 NL / min.

[0031] (3) Continuous casting process: During continuous casting, the tundish is cast with a stable liquid level, the nitrogen content in the molten steel increases by 0.0001%, and the total oxygen content in the molten steel is 0.0018%. During the normal continuous casting process, the molten steel volume in the tundish is 86.3% of the total molten steel volume when the tundish is full, and the molten steel volume in the tundish when changing the ladle during consecutive casting heats is 66.2% of the total molten steel volume when the tundish is full. Example 3

[0032] In this example, HP295 is smelted using the above control method, and the ladle volume is 200t. The specific implementation plan is as follows: (1) Converter process: In the converter slag blocking method, a front slag blocker and a slag stopper are used, and a slide gate is used for the rear slag blocking. The slag volume of the converter is 1.9 kg / t steel, and there is no re-blowing. During the tapping process, a carbon-aluminum composite deoxidation process is applied. When 15% of the steel has been tapped, 30 kg of coal-based carbon additive carbon powder is added per 100 tons of steel for pre-deoxidation. When 30% of the steel has been tapped, 300 kg of ferrosilicon aluminum is added per 100 tons of steel for deoxidation until the acid-soluble aluminum content in the molten steel reaches 0.0398%. When 95% of the steel has been tapped, the flow rate of the bottom blowing argon in the ladle is adjusted to 100 NL / min until the tapping is completed. The free oxygen at the end of the converter is 0.0503%.

[0033] (2) LF refining process: During LF refining, the operations of breaking the shell, adding slag-making materials, desulfurizing, increasing carbon, slag washing, and deoxidizing at the ladle furnace station adopt a strong blowing mode.

[0034] Before power supply, there is a slag crust in the ladle. The control range of blowing Ar is: 1000 NL / min for shell breaking; for the heats without tapping residue, when starting heating, the slag layer is relatively thin, and low or medium-low voltage is used, and the power-on time is 5 minutes; after the slag is basically formed, some slag-making materials can be appropriately added to ensure the submerged arc effect and increase the voltage level; the final slag of refining only needs to meet the slag-making requirements for aluminum-containing steel; during alloy addition, the control range of blowing Ar is: 800 NL / min, the exposed diameter of the molten steel is 500 mm, and the slag surface fluctuates without splashing. Stir for 4 minutes to make the inclusions float up sufficiently; for the heats with tapping residue, high voltage is directly used for power-on to increase the temperature; the deoxidizing aluminum for the molten steel should be added to the ladle as early as possible, and the number of aluminum additions is 2 times.

[0035] LF refining adopts a carbon-aluminum composite deoxidation slag-forming process; 0.15 kg / t steel of coal-based carbon additive is added for deoxidation and slag-making operations in the first 3 minutes during power supply, and then aluminum slag-making agent is added for white slag formation operations. After the white slag is formed, to ensure the white slag time, 0.05 kg / t steel of coal-based carbon additive is added during power supply, and the interval between each addition is 4 minutes.

[0036] During LF refining for uniform composition, temperature, feeding aluminum wire / carbon wire, and alloy addition, the control range of blowing Ar is: 800 NL / min, the exposed diameter of the molten steel is 500 mm, and the slag surface fluctuates without splashing. Stir for 4 minutes to make the inclusions float up sufficiently.

[0037] The Ar blowing control ranges for LF refining temperature measurement, sampling, oxygen determination, power supply, feeding titanium wire, calcium treatment, etc. are as follows: 400 NL / min, with a molten steel exposure diameter of 20 mm, and the static blowing mode is adopted.

[0038] From the end of calcium treatment in LF refining to tapping, the Ar blowing control range is: 100 NL / min.

[0039] (3)Continuous casting process: The continuous casting tundish adopts stable liquid level casting, with a nitrogen increase in molten steel of 0.0002% and a total oxygen content in molten steel of 0.0021%; during the normal continuous casting process, the molten steel amount in the tundish is 89.2% of the total molten steel amount when the tundish is full, and when changing the ladle during consecutive casting heats, the molten steel amount in the tundish is 68.3% of the total molten steel amount when the tundish is full. Example 4

[0040] In this example, HP295 is smelted using the above control method, and the ladle volume is 200 t. The specific implementation plan is as follows: (1)Converter process: The slag blocking method in the converter adopts front slag blocking plus a slag blocking plug, and the rear slag blocking adopts a slide plate for slag blocking. The slag volume in the converter is 2.0 kg / t of molten steel, and the supplementary blowing is carried out once; during the tapping process, a carbon-aluminum composite deoxidation process is applied. When 15% of the steel is tapped, 30 kg of coal-based carbon additive carbon powder is added per 100 tons of steel for pre-deoxidation; when 30% of the steel is tapped, 300 kg of ferrosilicon aluminum is added per 100 tons of steel for deoxidation until the acid-soluble aluminum content in the molten steel reaches 0.0391%; when 95% of the steel is tapped, the bottom blowing argon gas flow rate in the ladle is adjusted to 100 NL / min. By the end of tapping, the free oxygen at the converter end point is 552 ppm.

[0041] (2)LF refining process: For the LF refining process of entering the station to break the slag crust, adding slag-making materials, desulfurization, carbon addition, slag washing, and deoxidation, the strong blowing mode is adopted.

[0042] Before power supply, there is a slag crust in the ladle. The Ar blowing control range is: 1000 NL / min for breaking the crust; for the furnace without pouring residue, when starting heating, the slag layer is relatively thin, and low or medium-low gear voltages are used, and the power supply time is 5 minutes; after the slag is basically formed, some slag-making materials can be appropriately added to ensure the submerged arc effect and increase the voltage level; the final slag in refining only needs to meet the slag-making requirements for aluminum-containing steel; during the alloy addition period, the Ar blowing control range is: 800 NL / min, with a molten steel exposure diameter of 500 mm. Based on the slag surface fluctuation without splashing, stir for 4 minutes to make the inclusions fully float; for the furnace with pouring residue, directly use the high gear voltage to heat up; the deoxidation aluminum for molten steel should be added to the ladle as early as possible, and the aluminum supplement is carried out 2 times.

[0043] LF refining adopts the process of composite deoxidation and slag formation with carbon and aluminum; 0.15 kg / t of steel of coal-based carburizer is added for deoxidation and slag formation operation in the first 3 minutes during the power supply process, and then aluminum slag-making agent is added for white slag formation operation. After the white slag is formed, in order to ensure the white slag time, 0.05 kg / t of steel of coal-based carburizer is added during the power supply process, and the interval between each addition is 4 minutes.

[0044] During the processes of uniformizing composition, temperature, feeding aluminum wire / carbon wire, and adding alloy in LF refining, the Ar blowing control range is: 800 NL / min, and the exposed diameter of the molten steel is 500 mm. Based on the slag surface fluctuation without splashing, stir for 4 minutes to make the inclusions float up sufficiently.

[0045] During the processes of temperature measurement, sampling, oxygen determination, power supply, feeding titanium wire, calcium treatment, etc. in LF refining, the Ar blowing control range is: 400 NL / min, and the exposed diameter of the molten steel is 20 mm. The static blowing mode is adopted.

[0046] From the end of calcium treatment to tapping in LF refining, the Ar blowing control range is: 100 NL / min.

[0047] (3)Continuous casting process: The continuous casting tundish adopts stable liquid level casting, the nitrogen increase in the molten steel is 0.0003%, and the total oxygen content in the molten steel is 0.0024%; during the normal continuous casting process, the tundish molten steel amount is 86.9% of the total molten steel amount when the tundish is full, and the tundish molten steel amount during the ladle change for consecutive casting heats is 66.1% of the total molten steel amount when the tundish is full. Example 5

[0048] In this example, Q345R is smelted using the above control method, and the ladle volume is 200 t. The specific implementation plan is as follows: (1)Converter process: The slag blocking method in the converter adopts front slag blocking with a slag stopper and rear slag blocking with a slide plate. The slag entrainment amount of the converter is 1.8 kg / t of steel, and there is 1 supplementary blow; during the tapping process, the composite deoxidation process with carbon and aluminum is applied. When 15% of the steel is tapped, 30 kg of coal-based carburizer carbon powder is added per 100 tons of steel for preliminary deoxidation; when 30% of the steel is tapped, 300 kg of ferrosilicon aluminum is added per 100 tons of steel for deoxidation until the acid-soluble aluminum content in the molten steel reaches 0.0400%; when 95% of the steel is tapped, the bottom blowing argon gas flow rate in the ladle is adjusted to 100 NL / min until the tapping is completed, and the free oxygen at the converter end point is 563 ppm.

[0049] (2)LF refining process: In the LF refining process of entering the station to break the shell, adding slag-making materials, desulfurization, carburization, slag washing, and deoxidation, the strong blowing mode is adopted.

[0050] Before power supply, there is a slag crust in the ladle. The Ar blowing control range for shell breaking is 1000 NL / min; for ladle heats without tapping slag, the slag layer is relatively thin at the start of heating. Use low or medium-low voltage, and the power-on time is 5 minutes. After the slag is basically formed, some slag materials can be appropriately added to ensure the submerged arc effect and increase the voltage level; the final slag in refining only needs to meet the slag-making requirements for aluminum-containing steel. During alloy addition, the Ar blowing control range is 800 NL / min, and the exposed diameter of the molten steel is 500 mm. Based on the fluctuation of the slag surface without splashing, stir for 4 minutes to make inclusions float up sufficiently; for ladle heats with tapping slag, use high voltage to directly supply power for temperature increase; add deoxidizing aluminum to the ladle as early as possible, and the number of aluminum supplementation is 2 times.

[0051] LF refining adopts a carbon-aluminum composite deoxidation and slag-making process; add 0.15 kg / t of coal-based carbon increasing agent for deoxidation and slag-making operation within the first 3 minutes of the power supply process, and then add aluminum slag-making agent for making white slag. After the white slag is formed, to ensure the white slag time, add 0.05 kg / t of coal-based carbon increasing agent during the power supply process, with an interval of 4 minutes for each addition.

[0052] During LF refining for uniform composition, temperature, feeding aluminum wire / carbon wire, and alloy addition, the Ar blowing control range is 800 NL / min, and the exposed diameter of the molten steel is 500 mm. Based on the fluctuation of the slag surface without splashing, stir for 4 minutes to make inclusions float up sufficiently.

[0053] During LF refining for temperature measurement, sampling, oxygen determination, power supply, feeding titanium wire, calcium treatment, etc., the Ar blowing control range is 400 NL / min, and the exposed diameter of the molten steel is 20 mm, adopting a static blowing mode.

[0054] From the end of calcium treatment to tapping in LF refining, the Ar blowing control range is 100 NL / min.

[0055] (3) Continuous casting process: The continuous casting tundish adopts stable liquid level casting, with a nitrogen increase of 0.0003% in the molten steel and a total oxygen content of 0.0023% in the molten steel; during the normal continuous casting process, the molten steel volume in the tundish is 85.3% of the total molten steel volume when the tundish is full, and the molten steel volume in the tundish when changing the ladle for continuous casting heats is 65.2% of the total molten steel volume when the tundish is full.

[0056] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: The present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for controlling the total oxygen content in molten steel, characterized in that: The control method includes: hot metal pretreatment desulfurization, converter, LF refining, and continuous casting processes. The specific control parameters are as follows: (1) Converter process: During the tapping process, a carbon-aluminum composite deoxidation process is applied. When 5-15% of the steel is tapped, 0.5-3 kg / t of coal-based carburizer is added into the ladle for pre-deoxidation; when 15-30% of the steel is tapped, 1.5-3 kg / t of ferrosilicon aluminum is added into the ladle for deoxidation until the acid-soluble aluminum content in the molten steel reaches 0.0200-0.0400%; when 90-95% of the steel is tapped, the flow rate of bottom argon blowing in the ladle is adjusted to 20-100 NL / min. By the end of tapping, the free oxygen at the converter end point is ≤0.0600%; (2) LF refining process: Before power supply, the slag in the ladle forms a crust. The control range of Ar blowing for shell breaking is 600-1000 NL / min; for ladles without casting residue slag, when heating starts, the slag layer is relatively thin, and low or medium-low voltage is used, and the power supply time is 2-5 minutes; after the slag is basically formed, some slag materials can be appropriately added to ensure the submerged arc effect and increase the voltage level; the final slag in refining only needs to meet the slag-making requirements for aluminum-containing steel; during alloy addition, the control range of Ar blowing is 400-800 NL / min, and the exposed diameter of the molten steel is 400-500 mm. Based on the fluctuation of the slag surface without splashing, it is stirred for 3-4 minutes to make the inclusions float up sufficiently; for ladles with casting residue slag, high voltage is directly used for power supply to increase the temperature; the deoxidizing aluminum for the molten steel is added to the ladle as early as possible, and the number of aluminum addition replenishments is ≤2 times; (3) Continuous casting process: The continuous casting tundish adopts stable liquid level casting, with the nitrogen increase in the molten steel ≤0.0005% and the total oxygen content in the molten steel ≤0.0025%.

2. The control method for total oxygen in molten steel according to claim 1, characterized in that In the converter process described above, the slag volume is ≤2.5 kg / t of steel; the coal-based carburizer is carbon powder, and by mass percentage, C≥92%.

3. The control method for total oxygen in molten steel according to claim 1, characterized in that, In the converter process: The slag blocking method in the converter adopts front slag blocking plus a slag stopper, and the rear slag blocking adopts a slide plate for slag blocking; the number of reblows is ≤1 time.

4. The method for controlling the total oxygen content of molten steel according to any one of claims 1 to 3, characterized in that, In the LF refining process: LF refining adopts a carbon-aluminum composite deoxidation slag-making process; 0.05-0.15 kg / t of steel of coal-based carburizer is added for deoxidation slag-making operation in the first 3 minutes during power supply, and then aluminum slag-making agent is added for making white slag operation. After the white slag is formed, to ensure the white slag time, 0.025-0.05 kg / t of steel of coal-based carburizer is added during power supply, and the interval between each addition is 1-4 minutes.

5. The control method for total oxygen in molten steel according to any one of claims 1 to 3, characterized in that, In the LF refining process: For LF refining, the shell breaking, addition of slag-making materials, desulfurization, carburization, slag washing, and deoxidation at the LF refining station adopt a strong blowing mode.

6. The control method for total oxygen in molten steel according to any one of claims 1 to 3, characterized in that, In the LF refining process: During the processes of LF refining for uniform composition, temperature, feeding aluminum wire / carbon wire, and alloy addition, the control range of Ar blowing is 400-800 NL / min, the exposed diameter of the molten steel is 400-500 mm, and it is stirred for 3-4 minutes to make the inclusions float up sufficiently.

7. The method for controlling the total oxygen content of molten steel according to any one of claims 1 to 3, characterized in that In the LF refining process: During the processes of LF refining for temperature measurement, sampling, oxygen determination, power supply, feeding titanium wire, calcium treatment, etc., the control range of Ar blowing is 100-400 NL / min, the exposed diameter of the molten steel is 10-20 mm, and a static blowing mode is adopted.

8. The control method for total oxygen in molten steel according to any one of claims 1 to 3, characterized in that, In the LF refining process: From the end of calcium treatment in LF refining to tapping, the control range of Ar blowing is 20-100 NL / min.

9. The control method for total oxygen in molten steel according to any one of claims 1-3, characterized in that The continuous casting process: During the normal steel pouring process, the molten steel volume in the tundish is not less than 85% of the total molten steel volume when the tundish is full. When changing the tundish for continuous casting heats, the minimum molten steel volume in the tundish is not less than 65% of the total molten steel volume when the tundish is full.

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