Process for direct charging of thin slab caster with 300t converter smelted cold rolled steel sheet grade

Abstract

The present application relates to the technical field of steel metallurgy, and particularly discloses a 300t converter smelting cold-rolled plate steel thin slab continuous casting machine direct-up process method, which realizes the purpose of near direct-up of a 300t large converter smelting cold-rolled plate series steel thin slab continuous casting machine; cancels the RH vacuum process, cancels the LF refining process, and deep refining process time, carries out minimal slag modification on the 300t cold-rolled plate series steel after tapping, compresses the ladle steel holding period from 150min to 60min; utilizes the low carbon oxygen product of the converter 16, realizes stable aluminum yield, and realizes the slag at the argon station of the converter to reach the near terminal state level through the final point precise control (the final point carbon is less than or equal to 0.040%, the final point oxygen is less than or equal to 420ppm, and the final point phosphorus is less than or equal to 0.028%) and the innovative tapping deoxidization alloying process mode; develops a refining slag modification process; establishes calcium treatment and soft blowing standardized process parameters, realizes full denaturation of inclusions, reduces the surface skin defect of the cold-rolled plate, and improves the yield rate.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a direct-load process for smelting thin slabs of cold-rolled steel in a 300t converter using a continuous casting machine. Background Technology

[0002] The traditional process for smelting cold-rolled steel series grades (such as H01301 / H15801 / H16201 low-carbon aluminum-killed steel) in a 300-ton large converter is "converter → RH vacuum refining → LF refining → continuous casting". After tapping from the converter, the molten steel is hoisted to the RH vacuum refining station by overhead crane. The RH treatment time is 30-40 minutes for decarburization. Then, it is hoisted to the LF refining station by overhead crane. The LF refining treatment time is 60-65 minutes, which completes the white slag formation, desulfurization, and alloy fine-tuning. After final composition adjustment, it is finally hoisted to the continuous casting machine for casting. The entire refining process involves 150 minutes of ladle holding time. The long steel pressing time leads to a large temperature drop, resulting in a refining furnace heating time of ≥25 minutes and an electricity consumption of 36 kWh / t.

[0003] In traditional processes, the converter's endpoint control precision is insufficient, resulting in large fluctuations in the endpoint carbon content (0.03-0.08%) and the endpoint oxygen content (300-600ppm), leading to high consumption of deoxidizers (aluminum ingots, aluminum wire) and unstable aluminum yield. Inaccurate argon control during tapping leads to severe secondary oxidation of the molten steel. The LF refining slag modification effect is unsatisfactory, with high FeO content in the final slag (15-25%). Calcium treatment process parameters are unclear, lacking standardized control for parameters such as wire feed rate, soft blowing time, and soft blowing intensity, resulting in unstable inclusion modification and recurring turbulent flow in continuous casting. Therefore, it is necessary to explore a near-vertical process for smelting thin slabs of cold-rolled steel series in a 300t large converter to address the problems of insufficient control precision and poor smelting stability in existing converter smelting methods. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of this invention is to provide a direct casting process for 300t converter smelting of cold-rolled steel thin slabs on a continuous casting machine.

[0005] The technical solution adopted by this invention to solve its technical problem is: a direct-load process for continuous casting of thin slabs of cold-rolled steel in a 300t converter, comprising the following steps:

[0006] S1. Composition control: The mass percentage of steel composition control is as follows: C: 0.03-0.048%, Si: 0.035-0.10%, Mn: 0.12-0.15%, P≤0.028%, S≤0.004%, Als: 0.015-0.030%, and Mn / S≥25;

[0007] S2. Production organization conditions and rhythm control: Use Grade A steel ladles. The production rhythm is as follows: 15 minutes of converter blowing + 3 minutes of post-stirring + 5 minutes of converter steel feeding + 7 minutes of overhead crane hoisting + 30 minutes of simple refining treatment of steel ladle + 7 minutes of overhead crane hoisting + 20 minutes of continuous casting waiting for pouring. The total steel pressing time is controlled within 60 minutes.

[0008] S3. Raw material process control: The molten iron entering the furnace must have an S content of ≤0.001%, a temperature of ≥1280℃, and a silicon content of 0.25-0.35% by mass. Furthermore, the previous furnace in the converter must use desulfurized molten iron.

[0009] S4. Converter endpoint control: endpoint carbon ≤ 0.040%, endpoint oxygen ≤ 420ppm;

[0010] S5. Deoxidation and alloying sequence and argon control during steel tapping: Design of near-final state technology for ladle refining slag after converter tapping;

[0011] S6. Argon Station Operation: When the molten steel is turned on to the argon station, the argon gas is turned off. Sampling, temperature measurement, and slag sampling are carried out and sent for online testing and verification.

[0012] S7. Steel ladle refining slag upgrading process: Aluminum supply line is added according to the aluminum situation of the argon station, and the target aluminum mass percentage is controlled at 0.040%;

[0013] S8. The process is controlled according to rhythm;

[0014] S9. Calcium treatment process: Set calcium treatment conditions;

[0015] S10, Calcium Post-Soft Blowing Process: Immediately after wire feeding, reduce the ladle argon gas to soft blowing, with the exposed diameter of molten steel at 100-200mm, and the soft blowing time at 8-12min;

[0016] S11. Temperature and Covering Agent Control at the Outlet: Temperature is measured after soft blowing ends, and ladle covering agent is added before the ladle leaves the station.

[0017] Specifically, in step S2, the idle stop time of the Class A ladle is ≤50min, the casting residue is completely removed, the time from the completion of continuous casting to the slag removal is ≤15min, the argon gas permeability on both sides is good, and the use of new ladles, black ladles, or ladles with crusts on the bottom is strictly prohibited.

[0018] Specifically, in step S3, the scrap steel fed into the converter is adjusted according to the heat conditions, and no kiln slag is added directly or in the previous furnace batch; aluminum granules, modifiers, and calcium carbide are prepared in advance for the converter, with the aluminum granules having a particle size of 10-20mm, and fluorite and top slag limestone are prepared in the silo.

[0019] Specifically, in step S4, the converter uses an extremely low level of carbon-oxygen product 16 for endpoint control, with endpoint phosphorus ≤0.028%, post-stirring time ≤3min, TSO tapping temperature 1650-1660℃, and argon station temperature 1605-1615℃; the converter is not allowed to sweep the furnace mouth, and supplementary blowing is strictly prohibited.

[0020] Specifically, the near-final state technology of ladle refining slag after converter tapping in step S5 is as follows: 30 seconds after the start of converter tapping, add 1200 kg of lime and 100 kg of fluorite, adding the lime and fluorite together; when 2 / 3 of the steel has been tapped, add 300 kg of ferrosilicon, 350 kg of aluminum ingots, and 50 kg of calcium carbide; after tapping, add 50 kg of calcium carbide and 30 kg of aluminum granules to the slag surface, evenly; immediately after the steel flow is seen, turn on the bottom blowing argon gas in the ladle and add fluorite / top slag. The timing of adding fluorite must not be later than the top slag, and the top slag, fluorite, and alloys marked must be added before the end of tapping; reduce the argon gas flow when 2 / 3 of the steel has been tapped; when the steel flow is seen during tapping, turn on the bypass argon gas for 50 seconds, then adjust the argon gas flow to half the bypass argon gas flow and maintain it until the end of tapping; after tapping, adjust the argon gas flow under the furnace to a soft blowing state and turn it to the argon station.

[0021] Specifically, in step S7, large-scale stirring is strictly prohibited at the beginning of the ladle refining slag modification process. The bottom blowing flow should be kept to maintain the creeping motion of the refining slag, and the exposed diameter of the molten steel should be 300-400mm. For slag samples, pay attention to the slag condition and add lime, aluminum granules, and calcium carbide according to the slag condition. The goal is to produce yellow-white or dark green slag in the final slag. Observe the fluidity of the ladle slag. If the fluidity is poor, add 20-50kg of fluorite to improve it. The mass percentage of Mn entering the station should be controlled according to the target of 0.15%, and the mass percentage of Si in the tundish should be controlled according to the target of 0.05-0.10%. Ferrosilicon should be added according to the sampling situation at the station. When the S sample at the station is ≥0.004%, after slag adjustment, bypass stirring should be carried out according to the sulfur situation. The stirring time for each desulfurization should be ≤3min.

[0022] Specifically, the process in step S8 is controlled rhythmically as follows: when the remaining casting tonnage of the ladle is 280t, temperature is measured and samples are taken; at 250t, the sulfur content is tested, with a target of 0.007%, 300kg of lime is added, aluminum wire is added according to the target of 0.040%, and the process is bypassed and stirred for 3 minutes; at 220t, the outlet temperature is controlled at +20℃ and soft blowing is switched; at 180t, calcium treatment is performed for 400m and soft blowing is switched; at 100t, soft blowing is maintained until the ladle leaves the station.

[0023] Specifically, the calcium treatment conditions in step S9 are: a standard amount of calcium wire used is 400 meters.

[0024] Specifically, in step S11, the temperature measurement requires the superheat to be controlled at 17-27℃, the normal continuous casting station exit temperature is 1578-1588℃, and the station exit temperature is 3-5℃ higher than that of LF refining treatment; the amount of covering agent added is 180kg.

[0025] The present invention has the following beneficial effects:

[0026] The present invention presents a direct-up process for 300t converter smelting of cold-rolled steel thin slab continuous casting machine. The process flow is optimized, the RH vacuum refining process is eliminated, the ladle refining time is shortened from the traditional 60-80min to less than 30min, the total steel pressing time is shortened from 150min to less than 60min, and the production efficiency is increased by about 250%.

[0027] The present invention presents a direct-to-converter process for smelting thin slabs of cold-rolled steel in a 300t converter. This process improves the purity of the molten steel. Through precise control of the converter endpoint (endpoint carbon ≤ 0.040%, endpoint oxygen ≤ 420ppm), the aluminum yield is stable, and the total oxygen content in the steel is reduced. The LF refining slag is upgraded to yellow-white or dark green slag, significantly enhancing the desulfurization capacity. The sulfur content at the outlet is stably controlled at ≤ 0.004%, meeting the stringent requirement of S ≤ 0.004% for cold-rolled steel.

[0028] The present invention designs a direct-to-cast process for smelting thin slabs of cold-rolled steel in a 300t converter, which improves inclusion control, standardizes calcium treatment (400m calcium line) and soft blowing process (8-12min, exposed diameter of molten steel 100-200mm), fully modulates inclusions, reduces the content of non-metallic inclusions in the slab, reduces surface peeling defects of cold-rolled steel, and improves yield.

[0029] The present invention presents a direct-load process for smelting cold-rolled steel thin slabs in a 300t converter using a continuous casting machine. This process reduces costs, shortens ladle refining time, lowers power consumption from 33.25 kWh / t to 10 kWh / t, reduces kiln slag consumption by 20 kg / t, reduces refined lime by 5 kg / t, reduces argon consumption by 50%, and reduces electrode consumption by 0.18 kg / t.

[0030] The present invention presents a direct-start process for smelting cold-rolled steel thin slabs in a converter using a continuous casting machine. This process optimizes production organization, reduces the total pressing time to 60 minutes, lowers the overhead crane occupancy rate, accelerates the production pace, improves the matching between converter, refining, and continuous casting, and increases the number of consecutive castings per casting machine. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be described clearly, completely, and in further detail below. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] A near-vertical process for smelting thin slabs of cold-rolled steel series in a 300t large converter using a continuous casting machine includes the following steps:

[0033] (1) Applicable steel grades and composition control

[0034] This invention is applicable to the production of cold-rolled steel grades SPHC / RECC / HQ215B / DX51D+Z / Q235B in a 300-ton large converter. The mass percentage of the steel composition is controlled as follows: C: 0.03-0.048%, Si: 0.035-0.10%, Mn: 0.12-0.15%, P≤0.028%, S≤0.004%, Als: 0.015-0.030%, and Mn / S≥25.

[0035] (2) Production organization conditions and rhythm control

[0036] Use Class A ladles (no-load time ≤ 50 min), clean up casting residue, and ensure that the time from the completion of continuous casting to slag removal is ≤ 15 min. Ensure good argon gas permeability on both sides. It is strictly forbidden to use new ladles, black ladles, or ladles with crusts on the bottom. The production rhythm is organized as follows: 15 min of converter blowing + 3 min of post-stirring + 5 min of converter steel feeding + 7 min of overhead crane hoisting + 30 min of simple refining treatment of the ladle + 7 min of overhead crane hoisting + 20 min of waiting for continuous casting to start pouring (100t leaving the station). The total steel pressing time is controlled within 60 min.

[0037] (3) Raw material process control

[0038] The requirements for molten iron entering the furnace are: sulfur content ≤ 0.001%, temperature ≥ 1280℃, silicon content 0.25-0.35%, and desulfurized molten iron used in the previous heat. The amount of scrap steel entering the furnace should be adjusted according to the heat conditions. No kiln slag should be added directly or in the previous heat. Small packages of aluminum granules (10-20mm particle size), small packages of modifiers, and calcium carbide should be prepared in advance for the converter. Fluorite and top slag limestone should be prepared in the silo.

[0039] (4) Precise control of converter endpoint

[0040] The converter utilizes an extremely low carbon-oxygen product of 16 for precise endpoint control: endpoint carbon ≤0.040%, endpoint oxygen ≤420ppm, endpoint phosphorus ≤0.028%, post-stirring time ≤3min, TSO tapping temperature 1650-1660℃, and argon station temperature 1605-1615℃. Sweeping the furnace mouth is not allowed in the converter, and supplementary blowing is strictly prohibited. If the TSC temperature is too low, the temperature can be appropriately reduced to avoid overblowing, ensuring dynamic oxygen hit.

[0041] (5) Deoxidation and alloying sequence and argon control during steel tapping

[0042] Develop "near-final state technology for ladle refining slag after converter tapping". 30 seconds after the start of converter tapping, add 1200 kg of lime and 100 kg of fluorite (lime and fluorite added together). When 2 / 3 of the steel has been tapped, add 300 kg of ferrosilicon, 350 kg of aluminum ingots, and 50 kg of calcium carbide. After tapping, add 50 kg of calcium carbide and 30 kg of aluminum granules to the slag surface, evenly. Immediately after the steel flow is observed, turn on the bottom blowing argon gas in the ladle and add fluorite / top slag. The fluorite must be added no later than the top slag. The top slag, fluorite, and alloys listed must be added before the end of tapping. When 2 / 3 of the steel has been tapped, reduce the argon gas flow. When the steel flow is observed during tapping, turn on the bypass argon gas for 50 seconds, then adjust the argon gas flow to half the bypass argon flow and maintain it until the end of tapping. After tapping, adjust the argon gas flow under the furnace to a soft blowing state and turn it to the argon station.

[0043] (6) Argon station operation

[0044] During the verification process, the molten steel is brought to the argon station and the argon gas is shut off. Sampling, temperature measurement, and slag sampling (online testing) are then carried out. An overhead crane is contacted in advance to wait for the molten steel to be hoisted.

[0045] (7) Steel ladle refining slag upgrading process

[0046] Aluminum supply should be replenished according to the aluminum content at the argon station, with a target aluminum content controlled at 0.040%. Large-scale stirring is strictly prohibited at the start of treatment; maintain the bottom blowing flow rate to keep the refining slag undulating (exposed steel diameter 300-400mm). For slag samples, monitor the slag condition and add lime, aluminum granules, and calcium carbide as needed, aiming for a final slag that is yellowish-white or dark green. Observe the ladle slag fluidity; if poor, add 20-50 kg of fluorite to improve it. Mn content at the station should be controlled at the target of 0.15%, and Si content in the tundish at the target of 0.05-0.10%. Ferrosilicon should be added based on the station sampling. When sulfur content at the station sample is ≥0.004%, after slag adjustment, bypass stirring should be performed according to the sulfur content, with each desulfurization stirring time ≤3 minutes.

[0047] (8) Rhythm control

[0048] The process is controlled rhythmically: when the remaining casting tonnage of the ladle is 280t, temperature is measured and samples are taken; at 250t, the sulfur content is tested (target 0.007%), 300 kg of lime is added, aluminum wire is added according to the target of 0.040%, and the bypass is stirred for 3 minutes; at 220t, the outlet temperature is controlled at +20℃ and soft blowing is switched; at 180t, calcium treatment is performed for 400m and soft blowing is switched; at 100t, soft blowing is maintained until the ladle leaves the station.

[0049] (9) Calcium treatment process

[0050] The conditions for calcium treatment are: ① good slag improvement effect; ② the lifting and lowering pipe must be lowered; the standard calcium line usage is 400 meters, which can be increased by 50-100 meters if the slag condition is poor.

[0051] (10) Calcium post-soft blowing process

[0052] Immediately after wire feeding, reduce the ladle argon gas to soft blowing (exposed molten steel diameter 100-200mm). The blowing pressure should be based on the slag surface creep. Exposed molten steel is strictly prohibited. Soft blowing time is 8-12 minutes. Excessive stirring is strictly prohibited after wire feeding.

[0053] (11) Control of outlet temperature and covering agent

[0054] Temperature measurement is performed after soft blowing is completed. The superheat should be controlled at 17-27℃. The normal continuous casting temperature at the station is 1578-1588℃ (the station temperature is 3-5℃ higher than that of LF refining treatment). 180kg of ladle covering agent is added before the ladle leaves the station.

[0055] Example 1

[0056] The planned production capacity for 2026 is 10 million tons, with a direct-start ratio of 18.3% for low-carbon and low-silicon furnaces (the percentage of direct-start furnace runs from July 2025 to June 2026). Assuming 50% of this is implemented as near-direct-start, the following calculations are made: aluminum consumption is 1.92 kg / t, electricity consumption is 10 kWh / t, the comprehensive cost of steel materials increases by 26.37 yuan / t, kiln slag consumption decreases by 20 kg / t, refined lime decreases by 5 kg / t, argon consumption decreases by 50%, electrode consumption decreases by 0.18 kg / t, RH refractory material costs are reduced by 4.66 yuan / t, and KR refractory material and desulfurizer costs increase by 7 yuan / t. Based on the material prices in the June cost report (locked in using this month's prices), the annual benefits are calculated as follows:

[0057] Cost reduction benefit of aluminum consumption: 10 million tons × 18.3% × 50% × (2.61 kg / t - 1.92 kg / t) × 21,745.2 yuan / t = 13,728,900 yuan;

[0058] Electricity consumption reduction benefit: 10 million tons × 18.3% × 50% × (33.25 kWh / t - 10 kWh / t) × 0.5618 yuan / kWh = 11.9516 million yuan;

[0059] Cost reduction for refined lime: 10 million tons × 18.3% × 50% × 5 kg / t × 381.44 yuan / t = 1.745 million yuan;

[0060] Argon consumption cost reduction: 10 million tons × 18.3% × 50% × 1.728 m³ / t × 2.33 yuan / m³ * 50% = 1.842 million yuan;

[0061] Electrode consumption cost reduction: 10 million tons × 18.3% × 50% × (0.26 kg / t - 0.08 kg / t) × 13533.9 yuan / t = 2.229 million yuan;

[0062] Cost reduction for RH refractory materials: 10 million tons × 18.3% × 50% × 4.66 yuan / t = 4.2639 million yuan;

[0063] Input of refractory materials and desulfurizing agents: 10 million tons × 18.3% × 50% × 7 yuan / t = 6.405 million yuan;

[0064] Increased steel production costs: 10 million tons × 18.3% × 50% × 26.37 yuan / t = 24.1386 million yuan;

[0065] Kiln slag savings: 10 million tons × 18.3% × 20 kg / t × 642.69 yuan / t = 11.7612 million yuan;

[0066] Annual benefit = Cost reduction benefit of aluminum consumption + Cost reduction benefit of electricity consumption + Cost reduction of refined lime + Cost reduction of argon consumption + Cost reduction of electrode consumption + Cost reduction of RH refractory materials + - Investment in refractory materials and desulfurizers - Cost increase in iron and steel production + Savings in kiln slag = 13,728,900 yuan + 11,951,600 yuan + 1,745,000 yuan + 1,842,000 yuan + 2,229,000 yuan + 4,263,900 yuan - 6,405,000 yuan - 24,128,600 yuan + 11,761,200 yuan = 16,988,000 yuan.

[0067] This invention shortens the refining slag-making and desulfurization process time through converter low-carbon-oxygen product endpoint low-oxidation control technology, full-process sulfur control, near-final state technology of ladle refining slag after converter tapping, and segmented soft blowing control technology for ladle refining. This significantly reduces the refining cycle and refining heating time, resulting in substantial reductions in power and aluminum consumption, while also improving inclusions in the steel. It enables near-vertical continuous casting of thin slabs for cold-rolled steel series in a 300t large converter. The invention eliminates the RH vacuum process and the LF refining process, reducing the deep refining time. The slag modification after tapping of 300 tons of cold-rolled steel series is simplified, reducing the ladle loading cycle from 150 minutes to 60 minutes. Utilizing the low carbon-oxygen product of converter 16, and through precise control of the converter endpoint (endpoint carbon ≤0.040%, endpoint oxygen ≤420ppm, endpoint phosphorus ≤0.028%) and an innovative deoxidation and alloying process at the tapping stage, stable aluminum yield and near-final state of converter argon station slag are achieved. A refining slag modification process is developed to produce yellowish-white or dark green slag, achieving a sulfur content of ≤0.004% at the tapping stage, meeting the composition control requirements of Mn / S ≥25 for cold-rolled steel grades. Standardized process parameters for calcium treatment and soft blowing are established to achieve sufficient inclusion modification, reduce surface peeling defects in cold-rolled sheets, and improve yield.

[0068] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0069] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A direct-load process for continuous casting of thin slabs of cold-rolled steel in a 300t converter, characterized in that, Includes the following steps: S1. Composition control: The mass percentage of steel composition control is as follows: C: 0.03-0.048%, Si: 0.035-0.10%, Mn: 0.12-0.15%, P≤0.028%, S≤0.004%, Als: 0.015-0.030%, and Mn / S≥25; S2. Production organization conditions and rhythm control: Use Grade A steel ladles. The production rhythm is as follows: 15 minutes of converter blowing + 3 minutes of post-stirring + 5 minutes of converter steel feeding + 7 minutes of overhead crane hoisting + 30 minutes of simple refining treatment of steel ladle + 7 minutes of overhead crane hoisting + 20 minutes of continuous casting waiting for pouring. The total steel pressing time is controlled within 60 minutes. S3. Raw material process control: The molten iron entering the furnace must have an S content of ≤0.001%, a temperature of ≥1280℃, and a silicon content of 0.25-0.35% by mass. Furthermore, the previous furnace in the converter must use desulfurized molten iron. S4. Converter endpoint control: endpoint carbon ≤ 0.040%, endpoint oxygen ≤ 420ppm; S5. Deoxidation and alloying sequence and argon control during steel tapping: Design of near-final state technology for ladle refining slag after converter tapping; S6. Argon Station Operation: When the molten steel is turned on to the argon station, the argon gas is turned off. Sampling, temperature measurement, and slag sampling are carried out and sent for online testing and verification. S7. Steel ladle refining slag upgrading process: Aluminum supply line is added according to the aluminum situation of the argon station, and the target aluminum mass percentage is controlled at 0.040%; S8. The process is controlled according to rhythm; S9. Calcium treatment process: Set calcium treatment conditions; S10, Calcium Post-Soft Blowing Process: Immediately after wire feeding, reduce the ladle argon gas to soft blowing, with the exposed diameter of molten steel at 100-200mm, and the soft blowing time at 8-12min; S11. Temperature and Covering Agent Control at the Outlet: Temperature is measured after soft blowing ends, and ladle covering agent is added before the ladle leaves the station.

2. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that, In step S2, the idle time of the Class A ladle is ≤50min, the casting residue is completely removed, the time from the completion of continuous casting to the slag removal is ≤15min, the argon gas permeability on both sides is good, and the use of new ladles, black ladles, or ladles with crusts on the bottom is strictly prohibited.

3. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that... In step S3, the scrap steel fed into the converter is adjusted according to the heat conditions, and no kiln slag is added directly or in the previous furnace. Aluminum granules, modifiers, and calcium carbide are prepared in advance for the converter. The aluminum granules are 10-20mm in size, and fluorite and top slag limestone are prepared in the silo.

4. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that, In step S4, the converter uses an extremely low level of carbon-oxygen product 16 for endpoint control, with endpoint phosphorus ≤0.028%, post-stirring time ≤3min, TSO tapping temperature 1650-1660℃, and argon station temperature 1605-1615℃; the converter is not allowed to sweep the furnace mouth, and supplementary blowing is strictly prohibited.

5. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that... The near-final state technology of ladle refining slag after converter tapping in step S5 is as follows: 30 seconds after the start of converter tapping, add 1200 kg of lime and 100 kg of fluorite, adding them together; when 2 / 3 of the steel has been tapped, add 300 kg of ferrosilicon, 350 kg of aluminum ingots, and 50 kg of calcium carbide; after tapping, add 50 kg of calcium carbide and 30 kg of aluminum granules to the slag surface, evenly; immediately after the steel flow is seen, turn on the bottom blowing argon gas in the ladle and add fluorite / top slag. The timing of adding fluorite must not be later than the top slag, and the top slag, fluorite, and alloys marked must be added before the end of tapping; reduce the argon gas flow when 2 / 3 of the steel has been tapped; when the steel flow is seen during tapping, turn on the bypass argon gas for 50 seconds, then adjust the argon gas flow to half the bypass argon flow and maintain it until the end of tapping; after tapping, adjust the argon gas flow under the furnace to a soft blowing state and turn it to the argon station.

6. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that, In step S7, the ladle refining slag modification process must not involve large-scale stirring at the beginning of the treatment. Maintain the refining slag's creep by opening the bottom blowing flow rate, with the exposed diameter of the molten steel at 300-400mm. For slag samples, monitor the slag condition and add lime, aluminum granules, and calcium carbide as needed, aiming for a final slag that is yellowish-white or dark green. Observe the ladle slag's fluidity; if poor, add 20-50kg of fluorite to improve it. Control the mass percentage of Mn entering the station to the target of 0.15%, and the mass percentage of Si in the tundish to the target of 0.05-0.10%. Add ferrosilicon based on the incoming sampling. When the S sample at the station is ≥0.004%, after slag adjustment, bypass stirring should be performed according to the sulfur content, with each desulfurization stirring time ≤3min.

7. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that, The process in step S8 is controlled rhythmically as follows: when the remaining casting tonnage of the ladle is 280t, temperature is measured and samples are taken; at 250t, the sulfur content is tested, with a target of 0.007%, 300kg of lime is added, aluminum wire is added according to the target of 0.040%, and the process is bypassed and stirred for 3 minutes; at 220t, the outlet temperature is controlled at +20℃ and soft blowing is switched; at 180t, calcium treatment is performed for 400m and soft blowing is switched; at 100t, soft blowing is maintained until the ladle leaves the station.

8. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that, The calcium treatment conditions in step S9 are: the standard amount of calcium wire used is 400 meters.

9. The direct-load process for smelting cold-rolled steel sheet thin slabs in a 300t converter using a continuous casting machine according to claim 1, characterized in that, In step S11, the temperature measurement requires the superheat to be controlled at 17-27℃, the normal continuous casting outlet temperature is 1578-1588℃, and the outlet temperature is 3-5℃ higher than that of LF refining treatment; the amount of covering agent added is 180kg.