Method for reducing inclusions in tinplate MR-T2.5

Abstract

The invention relates to a method for reducing inclusions in tinplate MR-T2.5, and belongs to the technical field of metallurgy. Comprising the following steps: (1) molten iron KR refining; (2) smelting in a converter; (3) modifying tapping molten steel; (4) RH refining; (5) continuous casting; the tinplate comprises the following components: 0.050%-0.070% of C, less than or equal to 0.03% of Si, 0.20%-0.30% of Mn, less than or equal to 0.015% of P, less than or equal to 0.015% of S, 0.020%-0.060% of Als, less than or equal to 0.0035% of O and less than or equal to 0.0035% of N. By the adoption of the operation mode, the content of sulfur in steel and converter end point oxygen are stably controlled, modification, RH circulation, casting machine protection casting and a process water changing opening in the tapping process are designed, the impurity content w (O, N) of molten steel gas (oxygen and nitrogen) is smaller than or equal to 0.0070%, tinplate inclusion is effectively reduced, and the method has good popularization value.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for reducing inclusions in tinplate MR-T2.5. Background Art

[0002] MR-T2.5 tinplate is a type of electro-tinned steel sheet or coil, based on a cold-rolled low-carbon steel substrate. MR-T2.5 tinplate offers high hardness, strength, wear resistance, and corrosion resistance, making it widely used in industries such as food and beverage packaging, aerosol cans, the automotive industry, construction, home furnishings, and the power sector.

[0003] The presence of inclusions reduces the steel's plasticity, toughness, and fatigue properties, deteriorating its hot and cold working properties and some physical properties. The primary effect of inclusions on steel is the mismatch in deformation between the steel and the inclusion during processing, which leads to stress concentration in the metal surrounding the inclusion. This often causes the inclusions to break, creating voids in the steel, which can lead to cracks in the steel.

[0004] The existing method for controlling inclusions in tinplate MR-T2.5 shows the presence of 0.5-1.5 grade D type Al2O3 inclusions, most of which are at grade 1.0. Inclusion control is unstable, with holes and large-particle inclusions breaking the band. The mechanical properties are inconsistent, with the difference in edge-center performance exceeding 2HR30T (Rockwell surface hardness), the difference in bilateral performance exceeding 2HR30T, and the nitrogen content exceeding 0.0035%. Summary of the Invention

[0005] In view of the problem that inclusions are easily generated during the existing production of tinplate MR-T2.5, the present invention provides a method for reducing inclusions in tinplate MR-T2.5 to solve the above problem.

[0006] The technical solutions of the present invention are as follows: The present invention provides a method for reducing inclusions in tinplate MR-T2.5, comprising the following steps: (1) KR refining of molten iron; (2) converter smelting; (3) molten steel modification; (4) RH refining; (5) continuous casting; In the step (3), the molten steel is modified during the tapping process, and the oxygen content at the converter end is ≤0.0500%; when one-third of the steel is tapped, lime ≥1.74 kg / ton of steel, flux ≥0.65 kg / ton of steel, and modifier ≥1.30 kg / ton of steel are added; when the oxygen content at the converter end is >0.0500%, lime ≥2.17 kg / ton of steel, flux ≥1.09 kg / ton of steel, and modifier ≥1.74 kg / ton of steel are added. Deoxidizing alloy is added in the late stage of tapping to prevent nitrogen increase in the molten steel. Deoxidizing alloy is added when two-thirds of the steel is tapped, so that the molten steel has a high free oxygen content for most of the time, preventing nitrogen increase in the molten steel, and ensuring that the acid-soluble aluminum content of the RH refined steel liquid is 0.010%~0.025%; when adding deoxidizing alloy, the ladle bottom blowing is controlled to have a large flow rate of 60~80 Nm 3 / h, ensure that the deoxidized alloy melts without agglomeration, and adjust the bottom blowing to ≤10 Nm after adding the deoxidized alloy. 3 / h Maintain soft blowing state, and the diameter of liquid surface flipping should be based on the size of the bowl mouth to ensure that inclusions fully float up.

[0007] Furthermore, the tinplate includes the following components in mass percentage: C: 0.050% to 0.070%, Si≤0.03%, Mn: 0.20% to 0.30%, P≤0.015%, S≤0.015%, Als: 0.020% to 0.060%, O≤0.0035%, N≤0.0035%, and the balance is Fe.

[0008] Furthermore, in step (1), the conditions for the molten iron to arrive at the KR refining station are: it is strictly forbidden to add scrap steel such as crushed materials, horseshoes, and steel bar cuttings to the molten iron, the iron consumption is greater than 890 kg / ton of steel, and the molten iron temperature is greater than or equal to 1400°C.

[0009] Furthermore, in step (1), after the molten iron enters the KR station, desulfurization and slag removal are carried out. The KR adopts medium-low speed stirring to avoid further nitrogen addition to the molten iron. After the stirring is completed, an air blowing slag removal pipe is set at a distance of 20 cm above the molten iron liquid surface and an inclination of 30°. By blowing argon gas, more than 92% of the slag on the molten iron liquid surface is effectively removed, thereby preventing impurities from entering the converter and reducing pollution sources.

[0010] Furthermore, in step (2), scrap steel and molten iron are added to the converter, wherein the mass proportion of molten iron is 78% to 82% and the mass proportion of scrap steel is 18% to 22%; the scrap steel is high-quality scrap steel, mainly steel plate, supplemented by heavy scrap billets and rolled edge and rolled plate, and the nitrogen content of the scrap steel is controlled at 0.0045% to 0.0055%, wherein 10 to 15 tons of iron blocks are used for heat supplement; lime, magnesite, and sintered ore are added during the converter smelting process to form slag, and the alkalinity of the slag is 3.0 to 3.5, the converter terminal temperature is ≥1670°C, the terminal oxygen content is ≤0.0500%, and the terminal carbon content is 0.030% to 0.060%. The converter bottom blowing adopts the full-process argon blowing mode, and secondary oxygen blowing is strictly prohibited at the converter terminal. Wherein, alkalinity R = (CaO + MgO) / SiO2. Tinplate is not produced in the first furnace of the converter replenishment furnace and the first furnace of the casting. Among them, converter filling refers to the operation of maintaining the furnace bottom with filling materials after smelting.

[0011] Furthermore, in step (2), the ladle temperature is ≥1000°C, the ladle is made of ultra-low carbon steel, the ladle bottom is free of crust and residue, and cleaning of the ladle mouth is strictly prohibited throughout the process.

[0012] Furthermore, the chemical composition of the modifier is: SiO2≤5.00%, CaO≥18.00%, Al2O3≥18.00%, Al≥50.00%, H2O≤1.0%, P≤0.030%, S≤0.040%.

[0013] The chemical composition of the deoxidized alloy is: Al≥99.0%, Fe: 0.35%, Si: 0.22%, Cu: 0.02%, Ca: 0.03%, Mg: 0.05%, Zn: 0.03%, Ti: 0.01%.

[0014] Furthermore, after the steel is tapped, the converter is tilted 180 degrees, and all the high-sulfur slag in the converter is turned over, leaving no slag.

[0015] Furthermore, in step (4), the RH pure degassing time is ≥13 min, the vacuum time is ≥15 min, the circulation flow rate is 160~200 MPa, and the time from breaking the air to the start of casting is 20~40 min.

[0016] Furthermore, in step (5), the casting speed of the continuous casting machine is constant at 1.1 m / min, protective casting is adopted, the submerged nozzle is replaced in the 6th, 10th and 14th furnaces, the argon blowing flow rate of the ladle long nozzle is 50~150 L / min, the argon blowing flow rate of the stopper rod is 1~10 L / min, and the ladle is shut off when slag is seen to prevent slag from contaminating the molten steel.

[0017] The beneficial effects of the present invention are: The present invention provides a method for reducing tinplate MR-T2.5 inclusions. By adopting the above-mentioned operation mode, the sulfur content in the steel and the oxygen at the converter end point are stably controlled. The reforming, RH circulation, casting machine protection casting and process water change port are designed during the steel production process. The gas (oxygen and nitrogen) impurity content w (O, N) in the molten steel is ≤0.0070%, effectively reducing tinplate inclusions, and having great promotion value. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0019] Example 1 A method for reducing inclusions in tinplate MR-T2.5, comprising the following steps: (1) Hot metal KR refining It is strictly forbidden to add scrap steel such as crushed materials, horseshoes, and steel bar cut ends into molten iron. The iron consumption is 900 kg / ton of steel, and the molten iron temperature is 1400 ℃.

[0020] (2) Converter smelting KR uses low-speed stirring to avoid further nitrogen addition to the molten iron. After stirring is completed, an air-blowing slag-removing pipe is set 20 cm above the molten iron surface and at an inclination of 30°. By blowing argon gas, 92% of the slag on the molten iron surface is effectively removed, preventing impurities from entering the converter and reducing pollution sources.

[0021] The first heat of the converter reheating or casting cycle does not produce tinplate. The converter utilizes a double-slag process, removing significant amounts of phosphorus and sulfur in the early stages of smelting to prevent excessively high oxygen content at the final stage. Scrap steel is added to the converter, with molten iron accounting for 82% and scrap steel for 18%. The scrap steel used is high-quality, primarily steel plate, supplemented by heavy-duty scrap billets, edge mills, and plate mills. The nitrogen content of the scrap is controlled at 0.0055%, with 15 tons of iron blocks used for heat supplementation. During the converter smelting process, lime, magnesite, and sinter are added to form the slag. The slag has an alkalinity of 3.0, a final converter temperature of 1680°C, a final oxygen content of 0.0500%, and a final carbon content of 0.05%. The converter bottom blowing utilizes argon throughout the entire process, and secondary oxygen blowing is strictly prohibited at the final stage.

[0022] The ladle temperature is 1000 ℃, and the ladle uses ultra-low carbon steel. There is no crust or residue on the bottom of the ladle, and it is strictly forbidden to clean the ladle mouth during the entire process.

[0023] (3) Molten steel modification Molten steel is modified during the tapping process, with the final oxygen content in the converter at 0.0500%. When one-third of the steel is tapped, lime ≥2.0 kg / ton of steel, flux ≥0.90 kg / ton of steel, and modifier ≥1.50 kg / ton of steel are added. Deoxidizing alloys are added later in the tapping process to prevent nitrogen buildup in the molten steel. Taiwan aluminum is added when two-thirds of the steel is tapped, ensuring a high free oxygen content in the molten steel for most of the time and preventing nitrogen buildup. By the time the RH refined steel is finished, the acid-soluble aluminum content is 0.010%. When adding deoxidizing alloys, the ladle bottom blowing is controlled at a maximum flow rate of 60 Nm 3 / h, ensure that the alloy melts without agglomeration, and adjust the bottom blowing to 5 Nm after the alloy is added. 3 / h Maintain soft blowing state, and the diameter of liquid surface flipping should be based on the size of the bowl mouth to ensure that inclusions fully float up.

[0024] After the steel is tapped, the converter is tilted 180 degrees, and all the high-sulfur slag in the converter is turned over, leaving no slag.

[0025] (4) RH refining The RH pure degassing time is 15 min, the vacuum time is 17 min, the circulation flow rate is 200 MPa, and the time from breaking the air to the start of casting is 40 min.

[0026] (5) Continuous casting The constant casting speed of the continuous casting machine is 1.1 m / min, and protective casting is adopted. The submerged nozzle is replaced in the 6th, 10th and 14th furnaces of the casting sequence. The argon blowing flow rate of the long nozzle of the ladle is 50 L / min, and the argon blowing flow rate of the stopper rod is 3 L / min. The ladle is shut off when slag is seen to prevent slag from contaminating the molten steel.

[0027] 18 casting batches are required to realize long casting batch production.

[0028] Testing of the tinplate prepared in Example 1 revealed the following composition: C: 0.050%, Si: 0.025%, Mn: 0.27%, P: 0.014%, S: 0.013%, Als: 0.050%, O: 0.0033%, and N: 0.0034%. Example 1 effectively addressed the issues of Al2O3 inclusions and inconsistent mechanical properties. Al2O3 inclusions were eliminated, the difference in mechanical properties between the edge and center was within 2HR30T, the difference in mechanical properties between the two sides exceeded 2HR30T, and the nitrogen content was within 0.0035%.

[0029] Example 2 A method for reducing inclusions in tinplate MR-T2.5 comprises the following steps: (1) Hot metal KR refining It is strictly forbidden to add scrap steel such as crushed materials, horseshoes, and steel bar cut ends into the molten iron. The iron consumption is 890 kg / ton of steel, and the molten iron temperature is 1430 ℃.

[0030] (2) Converter smelting KR uses medium-speed stirring to avoid further nitrogen addition to the molten iron. After stirring is completed, an air-blowing slag-removing pipe is set up 20 cm above the molten iron surface and at an inclination of 30°. By blowing argon gas, 92% of the slag on the molten iron surface is effectively removed, preventing impurities from entering the converter and reducing pollution sources.

[0031] The first furnace of the converter reheating and the first furnace of the casting process do not produce tinplate. The converter adopts double slag operation to remove a large amount of phosphorus and sulfur in the early stage of smelting to avoid excessively high oxygen content at the end. Hot metal accounts for 78% of the total, while scrap steel accounts for 22%. High-quality scrap steel is used, primarily steel plate, supplemented by heavy-duty scrap billets, edge and plate. The nitrogen content of the scrap steel is controlled at 0.0045%, with 10 tons of iron blocks used for heat supplementation. During the converter smelting process, lime, magnesite, and sinter are added to form slag, achieving a slag alkalinity of 3.5. The converter endpoint temperature is 1670°C, the endpoint oxygen content is 0.0400%, and the endpoint carbon content is 0.06%. Argon is used throughout the converter bottom blowing process, and secondary oxygen blowing is strictly prohibited at the converter endpoint.

[0032] The ladle temperature is 1000 ℃, and the ladle uses ultra-low carbon steel. There is no crust or residue on the bottom of the ladle, and it is strictly forbidden to clean the ladle mouth during the entire process.

[0033] (3) Molten steel modification Molten steel is modified during the tapping process, with the final oxygen content in the converter at 0.0400%. When one-third of the steel is tapped, lime (≥1.74 kg / ton of steel), flux (≥0.65 kg / ton of steel), and modifier (≥1.30 kg / ton of steel) are added. Deoxidizing alloys are added later in the tapping process to prevent nitrogen buildup in the molten steel. Taiwan aluminum is added when two-thirds of the steel is tapped, ensuring a high free oxygen content in the molten steel for most of the time and preventing nitrogen buildup. By the time the RH refined steel is finished, the acid-soluble aluminum content is 0.015%. When adding deoxidizing alloys, the ladle bottom blowing is controlled at a maximum flow rate of 60 Nm 3 / h, ensure that the alloy melts without agglomeration, and adjust the bottom blowing to 5 Nm after the alloy is added. 3 / h Maintain soft blowing state, and the diameter of liquid surface flipping should be based on the size of the bowl mouth to ensure that inclusions fully float up.

[0034] After the steel is tapped, the converter is tilted 180 degrees, and all the high-sulfur slag in the converter is turned over, leaving no slag.

[0035] (4) RH refining The RH pure degassing time is 13 min, the vacuum time is 15 min, the circulation flow rate is 160 MPa, and the time from breaking the air to the start of casting is 20 min.

[0036] (5) Continuous casting The constant casting speed of the continuous casting machine is 1.1 m / min. The casting machine adopts protective casting. The submerged nozzle is replaced in the 6th, 10th and 14th furnaces of the casting sequence. The argon blowing flow rate of the long nozzle of the ladle is 150 L / min, the argon blowing flow rate of the stopper rod is 10 L / min, and the ladle is shut off when slag is seen to prevent slag from contaminating the molten steel.

[0037] 18 casting batches are required to realize long casting batch production.

[0038] Testing of the tinplate prepared in Example 2 revealed the following composition: C: 0.060%, Si: 0.03%, Mn: 0.30%, P: 0.015%, S: 0.014%, Als: 0.056%, O: 0.0033%, and N: 0.0032%. Example 2 effectively addressed the issues of Al2O3 inclusions and inconsistent mechanical properties. Al2O3 inclusions were eliminated, the difference in mechanical properties between the edge and center was within 2HR30T, the difference in mechanical properties between the two sides exceeded 2HR30T, and the nitrogen content was within 0.0035%.

[0039] Example 3 A method for reducing inclusions in tinplate MR-T2.5 comprises the following steps: (1) Hot metal KR refining It is strictly forbidden to add scrap steel such as crushed materials, horseshoes, and steel bar ends into the molten iron. The iron consumption is 900 kg / ton of steel, and the molten iron temperature is 1415 ℃.

[0040] (2) Converter smelting KR uses medium-speed stirring to avoid further nitrogen addition to the molten iron. After stirring is completed, an air-blowing slag-removing pipe is set up 20 cm above the molten iron surface and at an inclination of 30°. By blowing argon gas, 92% of the slag on the molten iron surface is effectively removed, preventing impurities from entering the converter and reducing pollution sources.

[0041] Tinplate is not produced during the first batch of converter reheating or casting. The converter utilizes a double-slag process, removing significant amounts of phosphorus and sulfur in the early stages of smelting to prevent excessively high oxygen content at the final stage. Scrap steel is added to the converter, with molten iron accounting for 78% and scrap steel 22%. High-quality scrap steel is used, primarily steel plate, supplemented by heavy-duty scrap billets, edge mills, and plate mills. Nitrogen content in the scrap is controlled at 0.0055%, with 10 tons of iron blocks used for heat supplementation. During the converter smelting process, lime, magnesite, and sinter are added to form slag. The slag has an alkalinity of 3.5, a final converter temperature of 1675°C, a final oxygen content of 0.0550%, and a final carbon content of 0.04%. Argon is used throughout the converter bottom blowing process, and secondary oxygen blowing is strictly prohibited at the converter end.

[0042] The ladle temperature is 1000 ℃, and the ladle uses ultra-low carbon steel. There is no crust or residue on the bottom of the ladle. It is strictly forbidden to clean the ladle mouth during the entire process.

[0043] (3) Molten steel modification Molten steel is modified during the tapping process, with an end-point oxygen content of 0.0550%. When one-third of the steel is tapped, lime (≥2.3 kg / ton of steel), flux (≥1.3 kg / ton of steel), and modifier (≥1.9 kg / ton of steel) are added. Deoxidizing alloys are added later in the tapping process to prevent nitrogen buildup in the molten steel. Taiwan aluminum is added when two-thirds of the steel is tapped, ensuring a high free oxygen content in the molten steel for most of the time and preventing nitrogen buildup. By the time the RH refined steel is finished, the acid-soluble aluminum content is 0.015%. When adding deoxidizing alloys, the ladle bottom blowing is controlled at a maximum flow rate of 80 Nm 3 / h, ensure that the alloy melts without agglomeration, and adjust the bottom blowing to 10 Nm after the alloy is added. 3 / h Maintain soft blowing state, and the diameter of liquid surface flipping should be based on the size of the bowl mouth to ensure that inclusions fully float up.

[0044] After the steel is tapped, the converter is tilted 180 degrees, and all the high-sulfur slag in the converter is turned over, leaving no slag.

[0045] (4) RH refining The RH pure degassing time is 17 min, the vacuum time is 21 min, the circulation flow rate is 200 MPa, and the time from breaking the air to the start of casting is 30 min.

[0046] (5) Continuous casting The continuous casting machine has a constant casting speed of 1.1 m / min and adopts protective casting. The submerged nozzles are replaced in the 6th and 10th castings. The argon blowing flow rate of the long nozzle of the ladle is 130 L / min, and the argon blowing flow rate of the stopper rod is 8 L / min. The ladle is shut off when slag is seen to prevent slag from contaminating the molten steel.

[0047] 12 casting batches are available to achieve long casting batch production.

[0048] Testing of the tinplate prepared in Example 3 revealed the following composition: C: 0.040%, Si: 0.02%, Mn: 0.25%, P: 0.013%, S: 0.012%, Als: 0.040%, O: 0.0035%, and N: 0.0035%. Example 3 effectively addressed the issues of Al2O3 inclusions and inconsistent mechanical properties. Al2O3 inclusions were eliminated, the difference in mechanical properties between the edges was within 2HR30T, the difference in mechanical properties between the edges was within 2HR30T, and the nitrogen content was within 0.0035%.

[0049] Example 4 A method for reducing inclusions in tinplate MR-T2.5, comprising the following steps: (1) Hot metal KR refining It is strictly forbidden to add scrap steel such as crushed materials, horseshoes, and steel bar cut ends into the molten iron. The iron consumption is 890 kg / ton of steel, and the molten iron temperature is 1400 ℃.

[0050] (2) Converter smelting KR uses low-speed stirring to avoid further nitrogen addition to the molten iron. After stirring is completed, an air-blowing slag-removing pipe is set 20 cm above the molten iron surface and at an inclination of 30°. By blowing argon gas, 92% of the slag on the molten iron surface is effectively removed, preventing impurities from entering the converter and reducing pollution sources.

[0051] Tinplate is not produced during the first converter reheat or the first casting. The converter utilizes a double-slag process, removing significant amounts of phosphorus and sulfur in the early stages of smelting to prevent excessively high oxygen content at the final stage. Scrap steel is added to the converter, with molten iron accounting for 82% and scrap steel for 18%. High-quality scrap steel is used, primarily steel plate, supplemented by heavy-duty scrap billets, edge mills, and plate mills. Nitrogen content in the scrap is controlled at 0.0045%, with 15 tons of iron blocks used for heat supplementation. During the converter smelting process, lime, magnesite, and sinter are added to form slag. The slag has an alkalinity of 3.0, a final converter temperature of 1680°C, a final oxygen content of 0.0600%, and a final carbon content of 0.035%. Argon is used throughout the converter bottom blowing process, and secondary oxygen blowing is strictly prohibited at the converter end.

[0052] The ladle temperature is 1000 ℃, and the ladle uses ultra-low carbon steel. There is no crust or residue on the bottom of the ladle, and it is strictly forbidden to clean the ladle mouth during the entire process.

[0053] (3) Molten steel modification Molten steel is modified during the tapping process, with the final oxygen content in the converter at 0.0600%. When one-third of the steel is tapped, lime (≥2.6 kg / ton of steel), flux (≥1.6 kg / ton of steel), and modifier (≥2.2 kg / ton of steel) are added. Deoxidizing alloys are added later in the tapping process to prevent nitrogen buildup in the molten steel. Aluminum is added when two-thirds of the steel is tapped, ensuring high free oxygen levels in the molten steel for most of the time and preventing nitrogen buildup. By the time the RH refined steel is finished, the acid-soluble aluminum content is 0.010%. When adding the deoxidizing alloy, aluminum, the ladle bottom blowing is controlled at a maximum flow rate of 80 Nm 3 / h, ensure that the alloy melts without agglomeration, and adjust the bottom blowing to 10 Nm after the alloy is added. 3 / h Maintain soft blowing state, and the diameter of liquid surface flipping should be based on the size of the bowl mouth to ensure that inclusions fully float up.

[0054] After the steel is tapped, the converter is tilted 180 degrees, and all the high-sulfur slag in the converter is turned over, leaving no slag.

[0055] (4) RH refining The RH pure degassing time is 19 min, the vacuum time is 23 min, the circulation flow rate is 200 MPa, and the time from breaking the air to the start of casting is 40 min.

[0056] (5) Continuous casting The constant casting speed of the continuous casting machine is 1.1 m / min, and protective casting is adopted. The submerged nozzle is replaced in the sixth furnace of the casting sequence. The argon blowing flow rate of the long nozzle of the ladle is 150 L / min, the argon blowing flow rate of the stopper rod is 10 L / min, and the ladle is shut off when slag is seen to prevent slag from contaminating the molten steel.

[0057] 10 casting batches are required to achieve long casting batch production.

[0058] Testing of the tinplate prepared in Example 4 revealed the following composition: C: 0.035%, Si: 0.01%, Mn: 0.23%, P: 0.014%, S: 0.011%, Als: 0.030%, O: 0.0035%, and N: 0.0034%. Example 4 effectively addressed the issues of Al2O3 inclusions and inconsistent mechanical properties. Al2O3 inclusions were eliminated, the difference in mechanical properties between the edges was within 2HR30T, the difference in mechanical properties between the edges was within 2HR30T, and the nitrogen content was within 0.0035%.

[0059] Comparative Example (1) The weight of molten iron is ≥205 tons and the temperature of molten iron is ≥1400℃.

[0060] (2) During the desulfurization stirring process, add 2000 kg to 2500 kg of desulfurizer, stirring time is 10 to 20 minutes, and the S content in the molten iron is ≤0.002%.

[0061] (3) The total converter charge is 260 tons, including 205 tons of molten iron and 55 tons of scrap steel. The scrap steel is rolled using high-quality scrap steel produced entirely in-house. The converter end temperature is ≥1670°C and the end oxygen content is 0.06% to 0.080%.

[0062] (4) Pure degassing in the RH off-furnace refining process is ≥7 min.

[0063] (5) When the temperature is 8℃<the superheat of the tundish≤20℃, the pulling speed is 1~1.6 m / min; when the temperature is 20℃<the superheat of the tundish≤35℃, the pulling speed is 0.9~1.6 m / min; when the temperature is 35℃<the superheat of the tundish≤40℃, the pulling speed is 0.9~1.5 m / min; when the temperature is 40℃<the superheat of the tundish≤45℃, the pulling speed is 0.9~1.4 m / min; when the temperature is 45℃<the superheat of the tundish≤50℃, the pulling speed is 0.9~1.3 m / min.

[0064] The tinplate prepared in the comparative example was tested and found to contain Al2O3 inclusions, unstable inclusion control, holes and large particle inclusions, inconsistent mechanical properties, edge-to-center performance differences exceeding 2HR30T, bilateral performance differences exceeding 2HR30T, and nitrogen content greater than 0.0035%.

[0065] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and substance of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be readily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A method for reducing inclusions in tinplate MR-T2.5, characterized in that: The steps include: (1) KR refining of molten iron; (2) converter smelting; (3) molten steel modification; (4) RH refining; (5) continuous casting; In the step (3), the molten steel is modified during the tapping process, and the oxygen content at the converter end point is ≤0.0500%; lime ≥1.74 kg / ton steel, flux ≥0.65 kg / ton steel, and modifier ≥1.30 kg / ton steel are added when one-third of the steel is tapped; when the oxygen content at the converter end point is >0.0500%, lime ≥2.17 kg / ton steel, flux ≥1.09 kg / ton steel, and modifier ≥1.74 kg / ton steel are added; deoxidizing alloy is added in the late stage of tapping, and deoxidizing alloy is added when two-thirds of the steel is tapped, and the acid-soluble aluminum content of the RH refined steel liquid is 0.010%~0.025%; when the deoxidizing alloy is added, the ladle bottom blowing is controlled to have a maximum flow rate of 60~80 Nm 3 / h, after adding deoxidizing alloy, adjust the bottom blowing ≤10 Nm 3 / h maintains soft blowing state.

2. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, wherein: Tinplate includes the following components in mass percentage: C: 0.050%~0.070%, Si≤0.03%, Mn: 0.20%~0.30%, P≤0.015%, S≤0.015%, Als: 0.020%~0.060%, O≤0.0035%, N≤0.0035%, and the balance is Fe.

3. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, wherein: In step (1), the conditions for the molten iron to the KR refining station are: it is strictly forbidden to add crushed materials, horseshoes, and steel bar scrap to the molten iron, the iron consumption is greater than 890 kg / ton of steel, and the molten iron temperature is greater than or equal to 1400°C.

4. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, wherein: In the step (1), after the molten iron enters the KR station, desulfurization and slag removal are carried out. The KR adopts medium-low speed stirring to avoid further nitrogen addition to the molten iron. After the stirring is completed, an air blowing slag removal pipe is set at a distance of 20 cm above the molten iron liquid surface and an inclination of 30 degrees. By blowing argon gas, more than 92% of the slag on the molten iron liquid surface is effectively removed, thereby preventing impurities from entering the converter and reducing pollution sources.

5. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, wherein: In the step (2), scrap steel and molten iron are added to the converter, wherein the molten iron accounts for 78% to 82% and the scrap steel accounts for 18% to 22%; the nitrogen content of the scrap steel is controlled at 0.0045% to 0.0055%, wherein 10 to 15 tons of iron blocks are used for heat supplement; lime, magnesite and sintered ore are added during the converter smelting process to make slag, the alkalinity of the slag is 3.0 to 3.5, the converter terminal temperature is ≥1670°C, the terminal oxygen content is ≤0.0500%, and the terminal carbon content is 0.030% to 0.060%. The converter bottom blowing adopts the full-process argon blowing mode, and secondary oxygen blowing is strictly prohibited at the converter terminal.

6. A method for reducing inclusions in tinplate MR-T2.5 according to claim 1, characterized in that: In the step (2), the ladle temperature is ≥1000°C, the ladle uses an ultra-low carbon ladle, the ladle bottom is free of crust and residue, and cleaning of the ladle mouth is strictly prohibited throughout the process.

7. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, wherein: The chemical composition of the modifier is: SiO2≤5.00%, CaO≥18.00%, Al2O3≥18.00%, MAl≥50.00%, H2O≤1.0%, P≤0.030%, S≤0.040%; the chemical composition of the deoxidation alloy is: Al≥99.0%, Fe: 0.35%, Si: 0.22%, Cu: 0.02%, Ca: 0.03%, Mg: 0.05%, Zn: 0.03%, Ti: 0.01%.

8. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, characterized in that: After the steel is tapped, the converter is tilted 180°, and all the high-sulfur slag in the converter is turned over, leaving no slag.

9. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, wherein: In the step (4), the RH pure degassing time is ≥13 min, the vacuum time is ≥15 min, the circulation flow rate is 160~200 MPa, and the time from breaking the air to the start of casting is 20~40 min.

10. The method for reducing inclusions in tinplate MR-T2.5 according to claim 1, wherein: In the step (5), the casting speed of the continuous casting machine is constant at 1.1 m / min, protective casting is adopted, the submerged nozzle is replaced in the 6th, 10th and 14th furnaces, the argon blowing flow rate of the ladle long nozzle is 50-150 L / min, the argon blowing flow rate of the stopper rod is 1-10 L / min, and the ladle is shut off when slag is seen to prevent the slag from contaminating the molten steel.