Operation method for adding sponge iron in converter to replace scrap steel

Abstract

The invention discloses an operation method for adding sponge iron to replace scrap steel in a converter, which comprises the following steps of: sequentially carrying out converter smelting, LF (ladle furnace) refining and continuous casting on steelmaking raw materials to obtain a continuous casting billet, correspondingly storing three types of sponge iron charge quantities of different sponge iron charge quantities, a small part, a half and all of the sponge iron charge quantities in a scrap steel station, and using the heat of the sponge iron, the silicon number si of molten iron is less than or equal to 0.25%; a small part of sponge iron is used, and half of the sponge iron can be used when the silicon number is smaller than or equal to 0.35; the silicon number si is smaller than or equal to 0.50% and can be completely replaced by sponge iron, a dust removal system is started during tapping of a tank pouring station, temperature measurement and sampling operation is carried out after tapping, when the measured temperature of molten iron is smaller than 1385 DEG C, the sponge iron and the sponge iron added into a loading machine are not allowed to be used, it is guaranteed that the sponge iron is free of moisture and not humid, and vehicle personnel need to coordinate the loading machine and a crane to walk and avoid each other; and the speed of the loader does not exceed 5 kilometers per hour, and the steel scrap adding walking route is strictly executed.

Description

Technical Field

[0001] The present invention belongs to the technical field of smelting, and particularly relates to an operation method for adding sponge iron instead of scrap steel in a converter. Background Art

[0002] The annual demand for scrap steel in China is more than 30 million tons, and about 26 million tons can be supplied domestically, with a shortage of 4 - 5 million tons. With the adjustment of the steel product structure in China, the proportion of electric furnace steel is increasing continuously, and the contradiction between supply and demand of high-quality scrap steel is tense, resulting in a growing market demand for direct reduced iron that can replace high-quality scrap steel.

[0003] Compared with traditional steelmaking raw materials, sponge iron contains less impurities, especially the content of harmful elements such as sulfur and phosphorus is relatively low, which helps to improve the quality of steel. During the steelmaking process, sponge iron can increase the air permeability of the furnace charge, making the reaction more sufficient. Since it can also dilute some residual elements in scrap steel and adjust the composition of steel, it is widely used in both electric furnace steelmaking and converter steelmaking.

[0004] For the converter process, affected by various factors such as the procurement channels, funds, and resources of the steel mill, the price of sponge iron is lower than that of purchased scrap steel. Moreover, when producing with sponge iron in the converter, the blowing time is short, shortening the production process and thus increasing the output.

[0005] In view of the above factors, an operation method for adding sponge iron instead of scrap steel in a converter is provided. By using sponge iron instead of scrap steel, the production efficiency can be improved, the production cost can be reduced, and the price of sponge iron is lower than that of scrap steel, thus achieving the goal of cost reduction. Summary of the Invention

[0006] The purpose of the present invention is to provide an operation method for adding sponge iron instead of scrap steel in a converter to solve the problems raised in the above background art.

[0007] The purpose of the present invention is achieved by the following technical solutions: An operation method for adding sponge iron instead of scrap steel in a converter, the operation method includes obtaining a continuous casting billet by successively passing the steelmaking raw materials through converter smelting, LF refining, and continuous casting processes;

[0008] Prepare 1 - 3 scrap steel tanks at the scrap steel station, corresponding to storing different sponge iron charging amounts, namely a small part, half, and all three sponge iron charging amounts;

[0009] For the furnace charges using sponge iron, the silicon number si of the hot metal ≤ 0.25%; for using a small part of sponge iron, the silicon number ≤ 0.35 can use half of the sponge iron; when the silicon number si ≤ 0.50%, all sponge iron can be used for substitution;

[0010] Add desulfurized hot metal, steel materials, and sponge iron into the converter. Right the converter body, lower the lance for blowing. Use a working oxygen pressure of 0.85 mpa, an oxygen flow rate of 11500 m³ / h, and a lance position of 1000 mm. After normal ignition, add desulfurization slag-making agent with a lance position of 1000 mm and blow for 3 minutes. Then add the desulfurization slag-making agent again with a lance position of 1200 mm. When blowing reaches 7 - 8 minutes, lift the lance when the slag is melted, tilt the converter to pour out the slag, pour out the high-sulfur slag that adsorbs the sulfur in the hot metal out of the furnace, and continue blowing until the molten slag is completely melted. During the slag melting process, add cold materials according to the flame condition, and at the same time, adjust the lance position according to the slag melting condition. After the slag is well melted, lower the lance to draw carbon. After the temperature and composition of the molten steel in the furnace meet the tapping requirements, carry out the tapping operation;

[0011] In the above operations, ensure that the sponge iron is free of moisture and not damp to avoid water vapor entering the steel and generating white spots;

[0012] LF refining: Refine with white slag operation. The molten steel must not be exposed throughout the process. Keep the argon flowing smoothly during the LF refining process; Add 0 - 100 kg of lime or fluorite for slag adjustment in the early stage of LF refining, and the argon flow rate is 240 - 280 NL / min; The xenon flow rate in the later stage of LF refining is 50 - 100 NL / min; Add 6 - 18 kg / heat of calcium wire before tapping. Control the S content index before LF tapping, with the temperature > 1615 °C. Do not add any slag materials after feeding the calcium wire to purify the molten steel. The soft blowing time ≥ 10 minutes to ensure that inclusions float up sufficiently;

[0013] Continuous casting: The molten steel outside the long nozzle must not be exposed to prevent secondary oxidation of the molten steel; Ensure the centering of the mold and constant casting speed, and use electromagnetic stirring to improve the surface quality of the billet;

[0014] During continuous casting, increase or decrease the secondary cooling water volume through the PLC to dynamically spray and cool the surface of the billet, making the surface temperature of each section of the billet as close as possible to the target temperature, so as to ensure the best thermal state;

[0015] Heating in the billet heating furnace: The heating temperature of the steel billet is 1080 - 1350 °C, the allowable temperature difference ≤ 50 °C, control the total heating time to 2 h, and the rolling start temperature is 1030 - 1050 °C. Prevent overheating, overburning, and decarburization, raise the temperature slowly, ensure the uniform heating temperature of the steel billet, and reduce the temperature difference.

[0016] Furthermore, the silicon number si of the hot metal ≤ 0.25%; Use a small amount of sponge iron, with a mass fraction accounting for 20 - 40% of the scrap ratio.

[0017] Furthermore, the hot metal temperature of the converter heat is higher than 1385 - 1500 °C. When the hot metal temperature is less than 1385 °C, the use of sponge iron is not allowed.

[0018] Furthermore, in the converter steelmaking process, the original charging system is maintained, where sponge iron and scrap steel are added first, and then hot metal is charged. The personnel guiding the vehicles need to coordinate the movements of the loaders and cranes and avoid each other. The speed of the loader shall not exceed 5 km / h, and the walking route for adding scrap steel shall be strictly followed.

[0019] Furthermore, the steel materials include steel edge waste and pig iron.

[0020] Furthermore, in the continuous casting process, the superheat is controlled between 20 - 35°C, weak cooling is adopted in the secondary cooling, and the cooling water distribution in the secondary cooling zone is controlled at 0.35 - 0.65 L / kg.

[0021] Furthermore, in the slab heating process, the temperature in the preheating section is <850°C, the target temperature in the preheating section is 825°C, the heating time in Heating Zone I > 1.5 h, the temperature in Heating Zone I is 800 - 1150°C, the heating time in Heating Zone II ≥ 1.5 h, the temperature in Heating Zone II is 1180 - 1200°C, the soaking temperature is 1180 - 1230°C, and the total heating time > 5.5 h.

[0022] Furthermore, there are four layout positions for the electromagnetic stirring devices during continuous casting: electromagnetic stirring for tundish heating (H - EMS), electromagnetic stirring in the mold (M - EMS), electromagnetic stirring in the cooling section (S - EMS), and electromagnetic stirring in the solidification section (F - EMS);

[0023] For the electromagnetic stirring for tundish heating (H - EMS), the current is 260 A and the frequency is 2 Hz; for the electromagnetic stirring in the mold (M - EMS), the current is 300 A and the frequency is 2 Hz; for the electromagnetic stirring in the cooling section (S - EMS), the current is 380 A and the frequency is 8 Hz; for the electromagnetic stirring in the solidification section (F - EMS), the current is 1100 A. The continuous casting billet is put into a slow - cooling pit for heat preservation for more than 24 h when the temperature > 550°C.

[0024] The application of the operation method of using sponge iron instead of scrap steel in the converter. By applying the operation method of using sponge iron instead of scrap steel in converter smelting, the production cost can be reduced, the smelting rate can be increased, so as to shorten the smelting time and improve the production efficiency, and ultimately achieve the purpose of improving the economic benefits.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] According to the silicon number produced by the converter, the present invention uses sponge iron to partially or completely replace scrap steel for production, so as to achieve the purpose of reducing the usage amount of scrap steel. Since the smelting time of sponge iron in the converter is short and the smelting rate is increased, the smelting time is shortened and the production efficiency is improved.

[0027] The present invention can improve production efficiency and reduce production costs by using sponge iron instead of scrap steel. The price of sponge iron is lower than that of scrap steel, thus achieving the goal of cost reduction. By using sponge iron instead of scrap steel in a steelmaking converter, the production cost per ton of steel can be reduced and the blowing time and smelting cycle can be shortened. According to the average price of sponge iron in 2024, which is 1,731.34 yuan per ton, and the price of purchased heavy scrap steel is 2,704.46 yuan per ton. Detailed implementation manners

[0028] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and make the above objects, features, and advantages of the present invention more obvious and understandable, the following further describes the detailed implementation manners of the present invention.

[0029] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0030] An operation method for using sponge iron instead of scrap steel in a converter. The operation method includes obtaining continuous casting billets by successively subjecting steelmaking raw materials to converter smelting, LF refining, and continuous casting processes;

[0031] Prepare 1 - 3 scrap steel bins at the scrap yard, corresponding to storing different sponge iron charging amounts, namely a small part, half, and all three sponge iron charging amounts;

[0032] For the furnace charges using sponge iron, the silicon number si of hot metal ≤ 0.25%; for using a small part of sponge iron, the silicon number ≤ 0.35 and half of sponge iron can be used; when the silicon number si ≤ 0.50%, all sponge iron can be used for substitution;

[0033] Add desulfurized hot metal, steel materials, and sponge iron into the converter, straighten the furnace body, lower the lance for blowing, use a working oxygen pressure of 0.85 mpa, an oxygen flow rate of 11,500 m³ / h, a lance position of 1,000 mm. After normal ignition, add desulfurization slag-making agent, with the lance position at 1,000 mm, blow for 3 minutes, then add desulfurization slag-making agent again, lance position: 1,200 mm. When blowing to 7 - 8 minutes, lift the lance to slag the furnace, shake the furnace to pour out the slag, pour out the high-sulfur slag that adsorbs the sulfur in the hot metal out of the furnace, continue blowing until the molten slag is thoroughly melted. During the slag melting process, add cold materials according to the flame condition, and at the same time, adjust the lance position according to the slag melting condition. After the slag is melted well, lower the lance to draw carbon. After the temperature and composition of the molten steel in the furnace meet the tapping requirements, perform the tapping operation;

[0034] In the above operations, ensure that the sponge iron has no moisture and is not damp to avoid water vapor entering the steel and generating white spots;

[0035] LF refining: The refining process uses white slag operation, and the molten steel must not be exposed throughout the process. Keep the argon gas flowing smoothly during the LF refining process; Add 0 - 100 kg of lime or fluorite to adjust the slag at the early stage of LF refining, and the argon gas flow rate is 240 - 280 NL / min; The xenon gas flow rate is 50 - 100 NL / min at the later stage of LF refining; Add 6 - 18 kg / ladle of calcium wire before tapping. Control the S content index before LF tapping, the temperature > 1615 °C. After feeding the calcium wire, do not add any slag materials to purify the molten steel, and the soft blowing time ≥ 10 min to ensure that inclusions float up sufficiently;

[0036] Continuous casting: The molten steel outside the long nozzle must not be exposed to prevent secondary oxidation of the molten steel; Ensure the centering of the mold and constant casting speed, and use electromagnetic stirring to improve the surface quality of the billet;

[0037] During continuous casting, increase or decrease the secondary cooling water volume through PLC to perform dynamic spray cooling on the surface of the billet, so that the surface temperature of each section of the billet is as close as possible to the target temperature, thereby ensuring the best thermal state;

[0038] Heating of the billet in the reheating furnace: The heating temperature of the steel billet is 1080 - 1350 °C, the allowable temperature difference ≤ 50 °C, control the total heating time to 2 h, and the rolling start temperature is 1030 - 1050 °C to prevent overheating, overburning and decarburization. Heat up slowly to ensure uniform heating temperature of the steel billet and reduce the temperature difference.

[0039] The silicon number si of the hot metal ≤ 0.25%; Use a small amount of sponge iron, and the mass fraction accounts for 20 - 40% of the scrap ratio.

[0040] The hot metal temperature of the converter heat is higher than 1385 - 1500 °C. When the hot metal temperature is less than 1385 °C, sponge iron is not allowed to be used.

[0041] The converter steelmaking process maintains the original charging system. First add sponge iron and scrap, and then tap the hot metal for production. The person guiding the vehicle should coordinate the walking of the loader and the crane. The speed of the loader shall not exceed 5 km / h, and strictly execute the walking route for adding scrap.

[0042] The steel materials include steel edge waste and pig iron.

[0043] The continuous casting process controls the superheat degree between 20 - 35 °C, and the secondary cooling uses weak cooling, and controls the cooling water distribution amount in the secondary cooling zone to be 0.35 - 0.65 L / kg.

[0044] The preheating section temperature of the billet heating process < 850 °C, the target of the preheating section is 825 °C, the heating I section time > 1.5 h, the heating I section temperature is 800 - 1150 °C, the heating II section time ≥ 1.5 h, the heating II section temperature is 1180 - 1200 °C, the soaking section temperature is 1180 - 1230 °C, and the total heating time > 5.5 h.

[0045] There are four layout positions of the electromagnetic stirring device in the continuous casting process, namely electromagnetic stirring for tundish heating (H-EMS), electromagnetic stirring for mold (M-EMS), electromagnetic stirring for cooling section (S-EMS), and electromagnetic stirring for solidification section (F-EMS);

[0046] For the electromagnetic stirring for tundish heating (H-EMS), the current is 260A and the frequency is 2Hz; for the electromagnetic stirring for mold (M-EMS), the current is 300A and the frequency is 2Hz; for the electromagnetic stirring for cooling section (S-EMS), the current is 380A and the frequency is 8Hz; for the electromagnetic stirring for solidification section (F-EMS), the current is 1100A. When the continuous casting billet is >550°C, it is put into a slow cooling pit for heat preservation for more than 24 hours. Specific Example 1:

[0048] An operation method of adding sponge iron instead of scrap steel in a converter. The operation method includes obtaining a continuous casting billet through the processes of converter smelting, LF refining, and continuous casting for the steelmaking raw materials in sequence;

[0049] Prepare 1 - 3 scrap steel bins at the scrap steel station, corresponding to storing different sponge iron charging amounts, namely a small part, half, and all three sponge iron charging amounts;

[0050] For the furnace charges using sponge iron, the silicon number si of the hot metal ≤ 0.25%; use a small part of sponge iron;

[0051] Add desulfurized hot metal, steel materials, and sponge iron into the converter, straighten the furnace body, lower the lance for blowing, use a working oxygen pressure of 0.85mpa, an oxygen flow rate of 11500m³ / h, a lance position of 1000mm. After normal ignition, add desulfurization slag-making agent, with the lance position at 1000mm, blow for 3 minutes, then add desulfurization slag-making agent again, lance position: 1200mm. When blowing to 7 - 8 minutes, lift the lance to slag the furnace, tilt the furnace to pour out the high-sulfur slag that adsorbs the sulfur in the hot metal, continue blowing until the molten slag is completely melted. During the slag melting process, add cold materials according to the flame condition, and at the same time, adjust the lance position according to the slag melting condition. After the slag is melted well, lower the lance to draw carbon. After the temperature and composition of the molten steel in the furnace meet the tapping requirements, perform the tapping operation;

[0052] In the above operation, ensure that the sponge iron has no moisture and is not damp to avoid water vapor entering the steel and generating white spots;

[0053] LF refining: Refining with white slag operation, the molten steel shall not be exposed throughout the process, and keep the argon flowing smoothly during LF refining; Add 60kg of lime or fluorite for slag adjustment in the early stage of LF refining, with an argon flow rate of 240NL / min; the xenon flow rate in the later stage of LF refining is 100NL / min; add 12kg / ladle of calcium wire before tapping. Control the S content index before LF tapping, temperature > 1615°C. After feeding the calcium wire, do not add any slag materials to purify the molten steel, and the soft blowing time is 18 minutes to ensure that inclusions float up sufficiently;

[0054] Continuous casting: The molten steel outside the long nozzle cannot be exposed to prevent secondary oxidation of the molten steel; ensure the centering of the mold, constant casting speed, and use electromagnetic stirring to improve the surface quality of the billet;

[0055] During continuous casting, increase or decrease the secondary cooling water volume through PLC, and perform dynamic spray cooling on the surface of the billet to make the surface temperature of each section of the billet as close as possible to the target temperature, so as to ensure the best thermal state;

[0056] Heating of the billet heating furnace: The heating temperature of the steel billet is 1080 - 1350 °C, the allowable temperature difference ≤ 50 °C, control the total heating time to 2 h, the rolling start temperature is 1030 - 1050 °C, prevent overheating, overburning and decarburization, raise the temperature slowly, ensure the uniform heating temperature of the steel billet, and reduce the temperature difference.

[0057] The silicon number si of the hot metal ≤ 0.25%; use a small part of sponge iron, accounting for 40% of the scrap ratio by mass fraction.

[0058] The hot metal temperature of the converter heat is higher than 1385 °C. When the hot metal temperature is less than 1385 °C, sponge iron is not allowed to be used.

[0059] The converter steelmaking process maintains the original charging system. First add sponge iron and scrap, and then tap the hot metal for production. The finger car personnel should coordinate the walking of the loader and the crane. The speed of the loader shall not exceed 5 km / h, and strictly execute the walking route for adding scrap.

[0060] The superheat degree is controlled within 25 °C during the continuous casting process. Weak cooling is adopted for secondary cooling, and the cooling water distribution amount in the secondary cooling zone is controlled to be 0.35 L / kg.

[0061] The temperature of the preheating section in the billet heating process < 850 °C, the target of the preheating section is 825 °C, the heating time of section I is 2.2 h, the heating temperature of section I is 950 °C, the heating time of section II is 4.3 h, the heating temperature of section II is 1170 °C, and the soaking section temperature is 1250 °C.

[0062] There are four layout positions of the electromagnetic stirring device during continuous casting, namely electromagnetic stirring for tundish heating (H - EMS), electromagnetic stirring for mold (M - EMS), electromagnetic stirring for cooling section (S - EMS) and electromagnetic stirring for solidification section (F - EMS);

[0063] For the electromagnetic stirring for tundish heating (H - EMS), the current is 260 A and the frequency is 2 Hz; for the electromagnetic stirring for mold (M - EMS), the current is 300 A and the frequency is 2 Hz; for the electromagnetic stirring for cooling section (S - EMS), the current is 380 A and the frequency is 8 Hz; for the electromagnetic stirring for solidification section (F - EMS), the current is 1100 A. The continuous casting billet > 550 °C enters the slow cooling pit for heat preservation for more than 24 h. Specific Example Two:

[0065] An operation method of adding sponge iron instead of scrap steel in a converter. The operation method includes obtaining continuous casting billets by successively subjecting steelmaking raw materials to converter smelting, LF refining, and continuous casting processes;

[0066] Prepare 1 - 3 scrap steel tanks at the scrap yard, corresponding to storing small amounts, half, and all three sponge iron charging amounts with different sponge iron charging amounts;

[0067] For the furnace charges using sponge iron, the silicon number of hot metal ≤ 0.35, and use half of the sponge iron;

[0068] Add desulfurized hot metal, steel materials, and sponge iron into the converter, swing the furnace body upright, lower the lance for blowing, use a working oxygen pressure of 0.85 mpa, an oxygen flow rate of 11500 m³ / h, a lance position of 1000 mm. After normal ignition, add desulfurization slag-making agent, with the lance position at 1000 mm, blow for 3 min, then add desulfurization slag-making agent again, lance position: 1200 mm. When blowing for 7 - 8 min, lift the lance when the slag melts, swing the furnace to pour out the slag, pour out the high-sulfur slag that adsorbs the sulfur in the hot metal out of the furnace, continue blowing until the molten slag is thoroughly melted. During the slag melting process, add cold charge temperature according to the flame condition. At the same time, adjust the lance position according to the slag melting condition. After the slag is well melted, lower the lance to draw carbon. After the temperature and composition of the molten steel in the furnace meet the tapping requirements, perform the tapping operation;

[0069] In the above operation, ensure that the sponge iron has no moisture and is not damp to avoid water vapor entering the steel and generating white spots;

[0070] LF refining: Refining with white slag operation, the molten steel shall not be exposed throughout the process, and keep the argon gas unobstructed during the LF refining process; Add 50 kg of lime or fluorite for slag adjustment in the early stage of LF refining, and the argon gas flow rate is 280 NL / min; The xenon gas flow rate in the later stage of LF refining is 70 NL / min; Add 12 kg / heat of calcium wire before tapping. Control the S content index before LF tapping, temperature > 1615 °C. After feeding the calcium wire, do not add any slag materials to purify the molten steel. The soft blowing time is 20 min to ensure that inclusions float up sufficiently;

[0071] Continuous casting: The molten steel outside the long nozzle shall not be exposed to prevent secondary oxidation of the molten steel; Ensure the centering of the mold, constant casting speed, and use electromagnetic stirring to improve the surface quality of the casting billet;

[0072] During continuous casting, increase or decrease the secondary cooling water volume through PLC to perform dynamic spray cooling on the surface of the casting billet, so that the surface temperature of each section of the casting billet is as close as possible to the target temperature, thereby ensuring the best thermal state;

[0073] Heating of the casting billet: The heating temperature of the steel billet is 1080 - 1350 °C, the allowable temperature difference ≤ 50 °C, control the total heating time to 2 h, and the rolling start temperature is 1030 - 1050 °C. Prevent overheating, overburning, and decarburization, heat up slowly, ensure the uniform heating temperature of the steel billet, and reduce the temperature difference.

[0074] When the molten iron temperature of the converter heat is higher than 1400 °C and lower than 1385 °C, the use of sponge iron is not allowed.

[0075] In the converter steelmaking process, the original charging system is maintained, adding sponge iron and scrap first, and then tapping molten iron for production. The finger personnel should coordinate the walking of the loader and the crane. The speed of the loader shall not exceed 5 km / h, and the scrap charging walking route shall be strictly implemented.

[0076] The superheat degree in the continuous casting process is controlled between 25 °C. Weak cooling is adopted in the secondary cooling, and the cooling water distribution amount in the secondary cooling zone is controlled at 0.65 L / kg.

[0077] In the billet heating process, the temperature of the preheating section is <850 °C, the target temperature of the preheating section is 825 °C, the heating time of section I is 2.2 h, the heating temperature of section I is 950 °C, the heating time of section II is 4.3 h, the heating temperature of section II is 1170 °C, and the soaking temperature is 1250 °C.

[0078] There are four layout positions of the electromagnetic stirring device during continuous casting, namely electromagnetic stirring for tundish heating (H-EMS), electromagnetic stirring in the mold (M-EMS), electromagnetic stirring in the cooling section (S-EMS) and electromagnetic stirring in the solidification section (F-EMS);

[0079] For the electromagnetic stirring for tundish heating (H-EMS), the current is 260 A and the frequency is 2 Hz. For the electromagnetic stirring in the mold (M-EMS), the current is 300 A and the frequency is 2 Hz. For the electromagnetic stirring in the cooling section (S-EMS), the current is 380 A and the frequency is 8 Hz. For the electromagnetic stirring in the solidification section (F-EMS), the current is 1100 A. The continuous casting billet is put into the slow cooling pit for heat preservation for more than 24 h when the temperature is >550 °C. Specific Embodiment Three:

[0081] An operation method for adding sponge iron instead of scrap in a converter. The operation method includes obtaining a continuous casting billet by subjecting steelmaking raw materials to converter smelting, LF refining, and continuous casting processes in sequence;

[0082] Prepare 1 - 3 scrap steel tanks at the scrap yard, corresponding to storing different sponge iron charging amounts, namely a small part, half, and all three sponge iron charging amounts;

[0083] When the silicon number si of the molten iron ≤ 0.50%, all sponge iron is used for substitution;

[0084] Add desulfurized iron, steel and sponge iron into the converter, shake the furnace body, lower the gun for blowing, use working oxygen pressure of 0.85 MPa, oxygen flow rate of 11500 m' / h, gun position of 1000 mm, after ignition is normal, add desulfurized slag-making agent, gun position of 1000 mm, blow for 3 minutes, then add desulfurized slag-making agent again, gun position: 1200 mm, blow for 7-8 minutes, slag is raised, shake the furnace to pour slag, pour out the high-sulfur slag that absorbs sulfur from the molten iron, continue blowing until the slag is completely melted, add cold material temperature according to the flame situation during the slag melting process, and adjust the gun position according to the slag melting situation. After the slag is melted, lower the gun to pull carbon, and the steel temperature and composition of the molten steel in the furnace meet the steel-making requirements before steel-making operation;

[0085] During the above operation, ensure that the sponge iron is free of moisture and damp to prevent moisture from entering the steel and causing white spots;

[0086] LF refining: white slag refining operation, molten steel must not be exposed throughout the whole process, and argon gas should be kept unobstructed during LF refining; 60kg lime or fluorite is added for slag adjustment in the early stage of LF refining, and the argon gas flow rate is 280NL / min; the xenon gas flow rate is 80NL / min in the later stage of LF refining; 6-18kg / furnace calcium wire is added before leaving the station, and the S content index is controlled before LF leaves the station, and the temperature is>1615℃. No slag is added after feeding the calcium wire to purify the molten steel, and the soft blowing time is ≥10min to ensure that the inclusions float fully;

[0087] Continuous casting: The molten steel outside the long nozzle cannot be exposed to prevent secondary oxidation of the molten steel; ensure the centering of the crystallizer, constant casting speed, and use electromagnetic stirring to improve the surface quality of the ingot;

[0088] During the continuous casting process, the amount of secondary cooling water is increased or decreased through PLC, and the casting surface is dynamically cooled by water spraying, so that the surface temperature of each section of the casting is as close to the target temperature as possible, thereby ensuring the best thermal state;

[0089] Heating in billet heating furnace: billet heating temperature is 1080~1350℃, the allowable temperature difference is ≤50℃, the total heating time is controlled to be 2h, the rolling temperature is 1030~1050℃, prevent overheating, overburning and decarburization, heat up slowly, ensure uniform billet heating temperature and reduce temperature difference.

[0090] When the molten iron temperature of the converter furnace is higher than 1500°C and lower than 1385°C, sponge iron is not allowed to be used.

[0091] The converter steelmaking process maintains the original loading system of adding sponge iron and scrap steel first, and then adding iron for production. The operator must coordinate the movement of the loader and crane. The loader speed must not exceed 5 kilometers per hour, and the scrap steel adding route must be strictly implemented.

[0092] The superheat degree in the continuous casting process is controlled between 20 - 35°C, weak cooling is adopted in secondary cooling, and the cooling water distribution in the secondary cooling zone is controlled at 0.65 L / kg.

[0093] In the slab heating process, the temperature in the preheating section is <850°C, the target temperature in the preheating section is 825°C, the heating time in Heating Section I is 2.2 h, the temperature in Heating Section I is 950°C, the heating time in Heating Section II is 4.3 h, the temperature in Heating Section II is 1170°C, and the soaking section temperature is 1250°C.

[0094] There are four layout positions of the electromagnetic stirring device during continuous casting, namely electromagnetic stirring for tundish heating (H - EMS), electromagnetic stirring in the mold (M - EMS), electromagnetic stirring in the cooling section (S - EMS), and electromagnetic stirring in the solidification section (F - EMS);

[0095] For the electromagnetic stirring for tundish heating (H - EMS), the current is 260 A and the frequency is 2 Hz. For the electromagnetic stirring in the mold (M - EMS), the current is 300 A and the frequency is 2 Hz. For the electromagnetic stirring in the cooling section (S - EMS), the current is 380 A and the frequency is 8 Hz. For the electromagnetic stirring in the solidification section (F - EMS), the current is 1100 A. The continuous casting billet is put into a slow cooling pit for heat preservation for more than 24 h when the temperature > 550°C.

[0096] In the above - mentioned embodiment, by using sponge iron instead of scrap steel, the production efficiency can be improved and the production cost can be reduced. The price of sponge iron is lower than that of scrap steel, thus achieving the goal of cost reduction.

[0097] In the above - mentioned embodiment, by using sponge iron instead of scrap steel in the steel - making converter, the production cost per ton of steel can be reduced and the blowing time can be shortened, thus shortening the smelting cycle. According to the average price of sponge iron of 1731.34 yuan / ton and the purchased heavy scrap steel of 2704.46 yuan / ton in 2024. See the following table:

[0098]

[0099] Specific Embodiment 4:

[0101] The application of the operation method of adding sponge iron instead of scrap steel in the converter. The operation method of adding sponge iron instead of scrap steel is applied in converter smelting. By using sponge iron instead of scrap steel, the production cost is reduced and the smelting rate is increased, thus achieving the effect of shortening the smelting time and improving the production efficiency, shortening the smelting time and achieving the purpose of improving the economic benefit.

[0102] It is obvious to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

[0103] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An operating method for replacing scrap steel with sponge iron in a converter, characterized in that: The operation method includes obtaining continuous casting billets by successively subjecting steelmaking raw materials to converter smelting, LF refining, and continuous casting processes; Prepare 1 - 3 scrap steel tanks at the scrap yard, corresponding to storing a small portion, half, and all three sponge iron charging amounts with different sponge iron charging amounts; For the furnace charges using sponge iron, the silicon number si of the hot metal ≤ 0.25%; for using a small portion of sponge iron, the silicon number ≤ 0.35, and half of the sponge iron can be used; when the silicon number si ≤ 0.50%, all sponge iron can be used for substitution; Add desulfurized hot metal, steel materials, and sponge iron to the converter, straighten the furnace body, lower the lance for blowing, use a working oxygen pressure of 0.85 mpa, an oxygen flow rate of 11500 m³ / h, a lance position of 1000 mm. After normal ignition, add desulfurization slag-making agent, with the lance position at 1000 mm, blow for 3 min, then add the desulfurization slag-making agent again, lance position: 1200 mm. When blowing for 7 - 8 min, lift the lance when the slag melts, shake the furnace to pour out the slag, pour out the high-sulfur slag that adsorbs the sulfur in the hot metal out of the furnace, continue blowing until the molten slag is thoroughly melted. During the slag melting process, add cold materials according to the flame condition, and at the same time, adjust the lance position according to the slag melting condition. After the slag is melted well, lower the lance to draw carbon. After the temperature and composition of the molten steel in the furnace meet the tapping requirements, perform the tapping operation; In the above operations, ensure that the sponge iron is free of moisture and not damp to avoid water vapor entering the steel and generating white spots; LF refining: Refining with white slag operation, the molten steel must not be exposed throughout the process, and keep the argon gas unobstructed during the LF refining process; Add 0 - 100 kg of lime or fluorite for slag adjustment in the early stage of LF refining, with an argon flow rate of 240 - 280 NL / min; the xenon flow rate in the later stage of LF refining is 50 - 100 NL / min; add 6 - 18 kg / heat of calcium wire before tapping. Control the S content index before LF tapping, temperature > 1615 °C. After feeding the calcium wire, do not add any slag materials to purify the molten steel, and the soft blowing time ≥ 10 min to ensure that inclusions float up sufficiently; Continuous casting: The molten steel outside the long nozzle must not be exposed to prevent secondary oxidation of the molten steel; ensure the centering of the mold, constant casting speed, and use electromagnetic stirring to improve the surface quality of the casting billet; During continuous casting, increase or decrease the secondary cooling water volume through PLC to perform dynamic spray cooling on the surface of the casting billet, so that the surface temperature of each section of the casting billet is as close as possible to the target temperature, thereby ensuring the best thermal state; Heating in the billet heating furnace: The heating temperature of the steel billet is 1080 - 1350 °C, the allowable temperature difference ≤ 50 °C, control the total heating time to 2 h, and the rolling start temperature is 1030 - 1050 °C to prevent overheating, overburning, and decarburization, heat up slowly, ensure the uniform heating temperature of the steel billet, and reduce the temperature difference.

2. The operation method of adding sponge iron instead of scrap steel in a converter according to claim 1, characterized in that: The silicon number si of the hot metal ≤ 0.25%; for using a small portion of sponge iron, the mass fraction accounts for 20 - 40% of the scrap steel ratio.

3. The operation method of adding sponge iron instead of scrap steel in a converter according to claim 2, characterized in that: The hot metal temperature of the converter furnace charge is higher than 1385 - 1500 °C. When the hot metal temperature is less than 1385 °C, it is not allowed to use sponge iron.

4. The operating method of adding sponge iron instead of scrap steel in a converter according to claim 3, characterized in that: The converter steelmaking process maintains the original charging system, first add sponge iron and scrap steel, and then tap the hot metal. The fingerboard operator should coordinate the walking of the loader and the crane. The speed of the loader shall not exceed 5 km / h, and strictly execute the walking route for adding scrap steel.

5. The operating method of adding sponge iron instead of scrap steel in a converter according to claim 4, characterized in that: The steel materials include steel edge waste and pig iron.

6. The operation method of adding sponge iron instead of scrap steel in a converter according to claim 5, characterized in that: The superheat degree in the continuous casting process is controlled between 20 - 35°C, and weak cooling is adopted in the secondary cooling. The cooling water distribution amount in the secondary cooling zone is controlled at 0.35 - 0.65 L / kg.

7. The operation method of adding sponge iron instead of scrap steel in a converter according to claim 6, characterized in that: In the slab heating process, the temperature in the preheating section is <850°C, and the target temperature in the preheating section is 825°C. The heating time in Heating Zone I > 1.5 h, the temperature in Heating Zone I is 800 - 1150°C, the heating time in Heating Zone II ≥ 1.5 h, the temperature in Heating Zone II is 1180 - 1200°C, the soaking temperature is 1180 - 1230°C, and the total heating time > 5.5 h.

8. The operation method of adding sponge iron instead of scrap steel in a converter according to claim 7, characterized in that: During the continuous casting process, there are four layout positions for the electromagnetic stirring device, namely the electromagnetic stirring for tundish heating (H - EMS), the electromagnetic stirring in the mold (M - EMS), the electromagnetic stirring in the cooling section (S - EMS), and the electromagnetic stirring in the solidification section (F - EMS); For the electromagnetic stirring for tundish heating (H - EMS), the current is 260 A and the frequency is 2 Hz. For the electromagnetic stirring in the mold (M - EMS), the current is 300 A and the frequency is 2 Hz. For the electromagnetic stirring in the cooling section (S - EMS), the current is 380 A and the frequency is 8 Hz. For the electromagnetic stirring in the solidification section (F - EMS), the current is 1100 A. The continuous casting billet enters the slow cooling pit for heat preservation for more than 24 h when the temperature > 550°C.

9. Use of the operation method of adding sponge iron instead of scrap steel in a converter according to any one of claims 1-8, characterized in that, Apply the operation method of replacing scrap steel with sponge iron in the converter as described in any one of claims 1 - 8 in converter smelting. Replace scrap steel with sponge iron to reduce production costs and improve the smelting rate, thereby shortening the smelting time and enhancing production efficiency, and achieving the purpose of improving economic benefits by shortening the smelting market and enhancing economic efficiency.

Images