Converter smelting process of total iron under high-temperature molten iron condition

Abstract

The present application belongs to the technical field of steel metallurgy converter smelting, and discloses a full-iron smelting process of a converter under high-temperature molten iron conditions. After the completion of the slag splashing and furnace protection operation, the slag is completely poured out and the molten iron is poured in. The initial temperature of the converter smelting reaction is controlled, the addition amount of lime, limestone, raw dolomite and dust ash briquetting is calculated according to the molten iron conditions and the end point control requirements of the steel grade. By adjusting the slag making system, the oxygen supply system, the temperature system and the end point system, the splashing in the full-iron smelting process of the converter under high-temperature molten iron conditions is effectively avoided by slowing down the temperature rise and prolonging the dephosphorization interval. The probability of the occurrence of environmental pollution, steel material loss, equipment damage accidents and the like caused by splashing is reduced, the stable smelting process is realized, the one-time hit rate of the full-iron smelting end point under high-temperature molten iron conditions is improved, the probability of the occurrence of end point composition or temperature inconsistency is reduced, and various disadvantages caused by the supplementary blowing and reprocessing are effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of converter smelting technology in iron and steel metallurgy, specifically a converter all-iron smelting process under high-temperature molten iron conditions. Background Technology

[0002] In converter smelting, molten iron and scrap steel are the main metal inputs. Molten iron serves as the primary heat source, providing physical and chemical heat, while scrap steel acts as a coolant to balance the heat of the molten pool. All-molten iron smelting is used when the machine is under maintenance or scrap steel resources are scarce; or when the molten iron temperature is too low and insufficient heat is required to incorporate scrap steel; or due to the quality requirements of the steel grade being produced and other process needs.

[0003] Compared to the scrap-addition furnace operation, smelting with molten iron is an unconventional operation, resulting in changes in thermal balance and kinetic conditions, and increased difficulty in process control. Due to the lack of the endothermic process of scrap melting, the initial molten pool temperature is high and the heating rate is rapid, easily leading to poor slag formation, metal splashing, and high final phosphorus levels. Without scrap obstruction in the molten pool, the mixing time of the molten metal is significantly shortened, the carbon-oxygen reaction rate is fast, and explosive splashing is prone to occur.

[0004] When the temperature of molten iron is low, the entire molten iron smelting process is relatively easy to control. When the temperature of molten iron is high, there is excess heat, and the difficulty of controlling the entire molten iron smelting process increases.

[0005] Chinese patent document CN113528738A discloses a method for smelting molten iron in a converter, which avoids splashing during the smelting process by adjusting the oxygen supply and slag-forming system, thus reducing the likelihood of environmental pollution and equipment damage caused by splashing. However, this method initially employs low-lance operation, accelerating the heating and stirring inside the molten pool, increasing the difficulty of slag formation and hindering splash control. This method also consumes a large amount of lime; calculations based on the lime usage in the examples show that the lime addition ranges from 36 to 46 kg / t of steel, resulting in high auxiliary material costs. Furthermore, the increased slag volume leads to a greater amount of iron carried away by the slag, which is detrimental to controlling steel consumption indicators.

[0006] Chinese patent document CN109423533A discloses a method for controlling the smelting of molten iron in a converter. This method involves adding 55-70% ore before and after the furnace is shaken, followed by smelting. This avoids splashing during the smelting process and prevents high-temperature over-oxidation at the final stage. However, this method is prone to causing splashing at the furnace mouth during molten iron addition, and under dry dust removal conditions, its application in the converter can easily lead to poor ignition and explosion accidents.

[0007] Controlling the initial temperature, balancing the temperature rise during the process, and stabilizing the smelting process have become the core issues in the operation of converter iron smelting. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a converter full-iron smelting process under high-temperature molten iron conditions. After the slag splashing and furnace protection operation is completed, all slag is poured out and mixed with molten iron. By controlling the initial temperature of the converter smelting reaction, the amount of lime, limestone, raw dolomite, and dust removal ash pellets added is calculated based on the molten iron conditions and the final control requirements of the steel grade. By adjusting the slag-forming system, oxygen supply system, temperature system, and final control system, and by slowing down the temperature rise and extending the dephosphorization range, splashing during the converter full-iron smelting process under high-temperature molten iron conditions is effectively avoided. This reduces the probability of environmental pollution, steel loss, and equipment damage caused by splashing, achieving a stable smelting process, improving the first-time hit rate of the final stage in high-temperature molten iron smelting, reducing the probability of inconsistencies in final composition or temperature, and effectively avoiding various drawbacks of re-blowing and reprocessing that affect steel quality, increase alloy costs, and exacerbate furnace lining erosion.

[0009] The technical solution adopted in this invention is as follows: a converter all-iron smelting process under high-temperature molten iron conditions, comprising the following steps:

[0010] (1) After the slag splashing and furnace protection operation is completed, all the slag is poured out and all the molten iron is added.

[0011] (2) Calculate the amount of bulk material to be added based on the iron conditions and the final control requirements of the steel grade. The bulk material includes lime, limestone, raw dolomite and dust removal ash briquettes. The iron temperature is 1370~1470℃.

[0012] (3) Process smelting control;

[0013] S1. Start blowing for 1 minute and 30 seconds, using a gun position of 1600-1650mm, and an oxygen supply intensity of 25000-26000m. 3 / h;

[0014] S2. Oxygen supply for 1 minute 30 seconds to 2 minutes 30 seconds, using a gun position of 1450 to 1550 mm, and an oxygen supply intensity of 26,000 to 28,000 m³ / h. 3 Feeding begins at 1 minute 30 seconds to 1 minute 50 seconds per hour, with lime accounting for 70-80% of the total amount, limestone accounting for 40-50% of the total amount, raw dolomite accounting for all of the total amount, and dust removal ash briquettes accounting for 70-80% of the total amount.

[0015] S3. Oxygen supply for 2 minutes 30 seconds to 4 minutes, using a gun position of 1400mm to 1450mm, with an oxygen supply intensity of 27000 to 30000 m³ / h. 3 / h, during which the remaining 20-30% lime is added;

[0016] S4. Oxygen supply of 4-10 minutes, using a gun position of 1200-1400mm, oxygen supply intensity of 28000-32000m. 3 / h, during which the remaining dust collection ash briquettes and limestone are added;

[0017] S5. Oxygen supply for 10 minutes – end point: lift the nozzle, using a nozzle position of 1100–1200 mm and an oxygen supply flow rate of 26000–28000 m³ / h. 3 / h. Since this application limits the molten iron temperature to 1370-1470℃, the process has more abundant heat. Therefore, in the converter operation control, corresponding adjustments are made to the lance position and oxygen supply intensity. The lance position generally shows a downward trend, while the oxygen supply intensity shows an upward trend. In the early stage of blowing, most of the slag and cold material are added, and the lance position is higher to slow down the reaction, avoid splashing, and help dephosphorization. In the middle stage of blowing, as the oxidation of ferrosilicon and manganese ends, the carbon-oxygen reaction begins to accelerate. Process dust ash briquettes and limestone are added in batches to balance the heating rate and promote the stable progress of the carbon-oxygen reaction. In the late stage of blowing, the lance position is lowered to make the composition and temperature more uniform.

[0018] Preferably, the molten iron conditions in step (2) include molten iron composition, temperature and loading amount; the steel grade endpoint control requirements include endpoint carbon, endpoint temperature and endpoint phosphorus content.

[0019] Preferably, in step (2), the amount of molten iron charged is 130 to 145 tons;

[0020] The composition of the molten iron is: carbon 4.2-5.0%, silicon 0.20-0.55%, manganese 0.25-45%, and phosphorus 0.11-0.15%. The above composition of the molten iron is by mass percentage.

[0021] Preferably, in step (2), the amount of lime added is calculated to be 16-19 kg / t steel, the amount of limestone added is 7-15 kg / t steel, and the amount of raw dolomite is 9-15 kg / t steel, based on the slag basicity requirements. Due to the influence of many factors such as molten iron temperature, molten iron composition, process operation, slag formation, and final temperature and composition, the amount of dust removal briquettes added will vary greatly. No limit is made here, and the amount added is calculated according to the specific situation.

[0022] Preferably, in step (2), the total iron content of the dust collector ash briquettes is ≥50%. To replace ore as a cold feedstock, there are requirements for the iron content of the dust collector ash briquettes, requiring a total iron content of ≥50%. There are no requirements for CaO content, but the CaO content must be within the range of 15-20%. Because the amount of ore added is relatively small under converter slag retention conditions, no difference was found between the dust collector ash briquettes and ore. However, under full-volume molten iron conditions, slag retention is not possible, and the amount of ore added is larger. By comparing the addition of dust collector ash briquettes and sintered ore, it was found that dust collector ash briquettes are more conducive to operation.

[0023] Preferably, in step (2), the endpoint control conditions for producing the steel grade are: endpoint carbon 0.08-0.13%, endpoint temperature 1610-1640℃, and endpoint phosphorus content ≤0.030%. The endpoint carbon and endpoint phosphorus contents mentioned above are mass percentages.

[0024] Preferably, in step S2, lime, limestone, raw dolomite, and dust removal ash briquettes are all added in one batch.

[0025] Preferably, in step S3, the lime is added in 2 to 3 batches, with the amount of lime added in each batch controlled at 1 to 3 kg / t of steel.

[0026] Preferably, in step S4, the remaining dust collector ash briquettes and limestone are added in batches. The amount of dust collector ash briquettes added in each batch is controlled at 2-5 kg / t of steel, with an interval of 50-70 seconds. The amount of limestone added in each batch is controlled at 1-3 kg / t of steel, with an interval of 1-3 minutes. Adding the remaining dust collector ash briquettes and limestone in batches at intervals, and implementing uniform material distribution, helps to maintain a stable temperature rise in the process, reduces the probability of process re-drying and splashing. If the cold material is too concentrated, the FeO in the slag will increase, which will easily cause splashing. Adding too much lime (or limestone) can easily cause the slag to re-dry.

[0027] Principle Analysis:

[0028] Under high-temperature molten iron conditions, replacing part of the lime with limestone significantly improves the control of the entire molten iron smelting process. Limestone burns down by about 50% during converter steelmaking, replacing some of the lime used for slag formation, and its price is much lower than lime. The CO2 produced at the steel-slag interface reacts with Fe in the molten iron to form FeO, which enters the slag, promoting slag formation and simultaneously increasing the oxidizing properties of the slag.

[0029] Limestone absorbs a large amount of heat during decomposition, which lowers the local temperature of the molten iron. The low temperature is conducive to dephosphorization. The cooling effect of limestone is about 3 to 4 times that of scrap steel, which can effectively balance the temperature of the molten pool.

[0030] Besides its excellent cooling properties, limestone also has several advantages: ① Limestone is priced around 100 yuan / ton, while lime is around 700 yuan / ton. When heated, limestone decomposes into CaO and CO2. Chemical calculations show that the ratio of lime to limestone is approximately 1:1.7, meaning that adding 1700 kg of limestone is equivalent to adding 1000 kg of lime, reducing auxiliary material costs by 0.53 yuan / kg. ② The CO2 produced during limestone decomposition acts as an oxidant, reacting with Fe to reduce oxygen consumption while increasing CO production. This benefits the recovery of coal gas and improves the utilization of coal gas energy.

[0031] ③Because limestone decomposes upon heating to produce nearly half of the CO2 gas, the total slag volume can be significantly reduced, thereby reducing the iron loss carried away by the slag and increasing the recovery of steel materials.

[0032] ④Because limestone decomposes when heated to produce gas, adding it during the blowing process can both thicken the foamy slag and stir the slag, promoting a more balanced reaction.

[0033] The dust collector ash briquettes described in this application are a type of solid waste utilization material. Made from compressed dust collector ash, they offer a cooling effect comparable to sintered ore, but at a price approximately 700 yuan / ton lower. These briquettes contain over 50% total iron, making them suitable as a cold feedstock. The CaO content is around 20%, and due to the abundant calorific value of the iron, a large amount of cold feedstock can be added. The dust collector ash briquettes also introduce a significant amount of CaO, which can replace some of the lime. In contrast, sintered ore is more expensive and introduces SiO2, increasing lime consumption. Comparing the two iron-containing cold feedstocks, dust collector ash briquettes are superior to sintered ore.

[0034] This application addresses the current situation of high-temperature molten iron charging in the furnace by slowing down the temperature rise in the early stage at a high lance position, thus extending the dephosphorization range. Furthermore, it involves adding limestone and dust collector briquettes in small batches in multiple batches to control the heating rate, prevent splashing, increase oxygen supply, accelerate FeO consumption, speed up decarburization, and shorten the smelting cycle. Through these processes, the slag formation effect is effectively guaranteed, achieving the goal of carbon retention and dephosphorization.

[0035] Compared with the prior art, the advantages of the present invention are:

[0036] (1) The present invention uses limestone to replace part of the lime, which can effectively reduce lime consumption and reduce the cost of auxiliary materials; it can effectively avoid the increase of slag due to excessive addition of auxiliary materials, reduce the consumption of steel materials, and use dust removal ash briquettes to replace sintered ore as cold material, which further reduces the amount of lime added while cooling the molten iron.

[0037] (2) By controlling the initial temperature of the converter smelting reaction, using a high lance position to slow down the temperature rise, and adding limestone and dust removal ash briquettes in multiple small batches, the probability of splashing during the converter smelting process under high temperature molten iron conditions is greatly reduced, thus avoiding the probability of accidents such as environmental pollution, metal loss, and equipment damage caused by splashing, and achieving the smooth operation of the converter smelting process.

[0038] (3) Furthermore, by slowing down the temperature rise, the dephosphorization range was extended, thereby improving the dephosphorization rate of converter iron smelting under high temperature conditions and avoiding various drawbacks caused by poor slag formation due to high initial temperature and rapid process temperature rise, resulting in high final phosphorus levels. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application are clearly and completely described below. In the following embodiments, the total iron content of the dust collector briquettes is ≥50%.

[0040] Example 1

[0041] This embodiment describes a converter-based all-iron smelting process under high-temperature molten iron conditions, producing steel grade HRB400E-1. The process uses 141.5 tons of molten iron at a temperature of 1431℃. The molten iron composition is: carbon 4.77%, silicon 0.33%, manganese 0.27%, and phosphorus 0.138%. The auxiliary material consumption for this furnace is: lime 2405 kg, limestone 1450 kg, raw dolomite 1400 kg, and dust collection ash briquettes 10955 kg.

[0042] The blowgun was initially positioned at 1650mm, and lowered to 1600mm in 1 minute and 30 seconds, providing an oxygen supply intensity of 25,000 m³ / h. 3 / h; 7670kg of dust collector briquettes are added at 1 minute 40 seconds; 1690kg of lime, 1400kg of raw dolomite, and 600kg of limestone are added at 1 minute 50 seconds; the nozzle is lowered to 1550mm at 2 minutes; and to 1500mm at 2 minutes 30 seconds, with an oxygen supply intensity of 26500m. 3 / h; Add 265kg of lime at 2 minutes and 30 seconds, lower the nozzle to 1450mm at 3 minutes, add 250kg of lime at 3 minutes and 10 seconds, lower the nozzle to 1400mm at 4 minutes and add 200kg of lime, oxygen supply intensity 28000m 3 / h; 280kg limestone added at 4 minutes 40 seconds, 620kg dust collector briquettes added at 5 minutes 30 seconds, 550kg dust collector briquettes added at 6 minutes 30 seconds, 265kg limestone added at 7 minutes, 650kg dust collector briquettes added at 7 minutes 20 seconds, 155kg limestone added at 8 minutes, 570kg dust collector briquettes added at 8 minutes 10 seconds, 610kg dust collector briquettes added at 9 minutes, 150kg limestone added at 9 minutes 20 seconds, and 285kg dust collector briquettes added at 9 minutes 50 seconds; oxygen supply intensity 28500m 3 / h; 10 minutes to lower the gun position to 1350mm, 10 minutes 20 seconds to 1300mm, 10 minutes 45 seconds to 1250mm, 11 minutes to 1200mm, 11 minutes 40 seconds to 1150mm, oxygen supply intensity 27000m 3 / h.

[0043] Oxygen supply time was 756 seconds, the final temperature was 1622℃, and the final carbon content was 0.097% and phosphorus content was 0.030%.

[0044] Example 2

[0045] This embodiment describes a converter smelting process for iron production under high-temperature molten iron conditions, producing steel grade HRB500E-1. The process yields 141.4 tons of molten iron at a temperature of 1463℃. The molten iron composition is: carbon 4.83%, silicon 0.38%, manganese 0.27%, and phosphorus 0.135%. The auxiliary material consumption for this furnace is: lime 2550 kg, limestone 2010 kg, raw dolomite 1360 kg, and dust collection ash briquettes 10480 kg.

[0046] The blowgun was initially positioned at 1620mm, and lowered to 1570mm after 1 minute, providing an oxygen supply intensity of 25300m³. 3 / h; 8300kg of dust collector briquettes are added at 1 minute 40 seconds; 2000kg of lime, 1360kg of raw dolomite, and 1000kg of limestone are added at 1 minute 45 seconds; the nozzle is lowered to 1520mm at 1 minute 50 seconds; and to 1470mm at 2 minutes 20 seconds, with an oxygen supply intensity of 26700m. 3 / h; Add 300kg of lime at 2 minutes and 30 seconds, lower the nozzle to 1420mm at 3 minutes, add 250kg of lime at 3 minutes and 30 seconds, lower the nozzle to 1370mm at 4 minutes, oxygen supply intensity 28200m 3 / h; Add 275kg limestone at 4 minutes, add 235kg limestone at 4 minutes and 40 seconds, lower the nozzle to 1320mm at 5 minutes, add 260kg limestone at 5 minutes and 10 seconds, add 500kg dust collector briquettes at 5 minutes and 50 seconds, add 540kg dust collector briquettes at 6 minutes and 45 seconds, add 550kg dust collector briquettes at 7 minutes and 40 seconds, add 240kg limestone at 8 minutes and lower the nozzle to 1270mm, add 300kg dust collector briquettes at 8 minutes and 35 seconds, add 290kg dust collector briquettes at 9 minutes and 30 seconds, lower the nozzle to 1220mm at 9 minutes and 40 seconds, oxygen supply intensity 28300m 3 / h; 10 minutes 30 seconds to lower the nozzle to 1170mm, 11 minutes 30 seconds to lower it to 1120mm, oxygen supply intensity 26300m 3 / h.

[0047] Oxygen supply time was 741 seconds, the final temperature was 1615℃, and the final carbon content was 0.092% and phosphorus content was 0.026%.

[0048] Example 3

[0049] This embodiment describes a converter smelting process for iron production under high-temperature molten iron conditions, producing steel grade HRB500E-2. The process yields 142.3 tons of molten iron at a temperature of 1397℃. The molten iron composition is: carbon 4.18%, silicon 0.27%, manganese 0.26%, and phosphorus 0.126%. The auxiliary material consumption for this furnace is: 2560 kg of lime, 1000 kg of limestone, 1580 kg of raw dolomite, and 9500 kg of dust collection briquettes.

[0050] The blowgun was initially positioned at 1600mm, and lowered to 1550mm in 1 minute and 30 seconds, with an oxygen supply intensity of 25200 m³ / h. 3 / h; Add 7100kg of dust collector briquettes at 1 minute 40 seconds, add 1800kg of lime, 1580kg of raw dolomite, and 400kg of limestone at 1 minute 50 seconds, lower the nozzle to 1500mm at 2 minutes, and lower it to 1450mm at 2 minutes 30 seconds, with an oxygen supply intensity of 27100m. 3 / h; Add 220kg of lime at 2 minutes and 35 seconds, lower the lance to 1400mm at 3 minutes, add 265kg of lime at 3 minutes and 15 seconds, add 275kg of lime at 3 minutes and 55 seconds, oxygen supply intensity 28400m 3 / h; 180kg limestone was added at 4 minutes 30 seconds, 600kg dust collector briquettes at 5 minutes 30 seconds, 570kg dust collector briquettes at 6 minutes 30 seconds, 190kg limestone at 7 minutes 20 seconds, 550kg dust collector briquettes at 7 minutes 35 seconds, 680kg dust collector briquettes at 8 minutes 40 seconds, and 220kg limestone at 9 minutes 30 seconds. The nozzle was lowered to 1350mm at 9 minutes 40 seconds, with an oxygen supply intensity of 28500m. 3 / h; 10 minutes 10 seconds to lower the nozzle to 1300mm, 10 minutes 30 seconds to 1250mm, 10 minutes 50 seconds to 1200mm, 11 minutes 25 seconds to 1150mm, oxygen supply intensity 26400m 3 / h.

[0051] Oxygen supply time was 734 seconds, the final temperature was 1624℃, and the final carbon content was 0.081% and phosphorus content was 0.030%.

[0052] Example 4

[0053] This embodiment describes a converter smelting process for iron production under high-temperature molten iron conditions, producing Q235B steel. The process uses 140.1 tons of molten iron at a temperature of 1427℃. The iron composition is: carbon 4.31%, silicon 0.30%, manganese 0.26%, and phosphorus 0.121%. The auxiliary material consumption for this furnace is: 2500 kg of lime, 1350 kg of limestone, 1740 kg of raw dolomite, and 9960 kg of dust collection briquettes.

[0054] The blowgun was initially positioned at 1650mm, and lowered to 1600mm in 1 minute and 20 seconds, providing an oxygen supply intensity of 25300m. 3 / h; 7470kg of dust collector briquettes are added at 1 minute 30 seconds, followed by 1875kg of lime, 1740kg of raw dolomite, and 620kg of limestone at 1 minute 40 seconds. The nozzle is lowered to 1550mm at 2 minutes and then to 1500mm at 2 minutes 30 seconds, with an oxygen supply intensity of 26800m. 3 / h; 2 minutes 40 seconds to add 260 kg of lime, 3 minutes to lower the nozzle to 1450 mm, 3 minutes 15 seconds to add 195 kg of lime, 3 minutes 55 seconds to add 170 kg of lime, oxygen supply intensity 28300 m 3 / h; 4 minutes lower the nozzle to 1400mm, 4 minutes 25 seconds add 225kg limestone, 5 minutes 10 seconds add 240kg limestone, 5 minutes 30 seconds lower the nozzle to 1350mm, 6 minutes 10 seconds add 450kg dust collector briquettes, 7 minutes add 530kg dust collector briquettes, 7 minutes 40 seconds add 265kg limestone, 8 minutes 05 seconds add 610kg dust collector briquettes, 9 minutes add 480kg dust collector briquettes, 9 minutes 40 seconds lower the nozzle to 1300mm, 9 minutes 50 seconds add 420kg dust collector briquettes, oxygen supply intensity 28100m 3 / h; 10 minutes 30 seconds to lower the nozzle to 1250mm, 11 minutes 40 seconds to lower it to 1200mm, oxygen supply intensity 26600m 3 / h.

[0055] Oxygen supply time was 740 seconds, the final temperature was 1631℃, and the final carbon content was 0.093% and phosphorus content was 0.025%.

[0056] Example 5

[0057] This embodiment describes a converter smelting process for iron production under high-temperature molten iron conditions, producing Q335B steel. The process involves 134.7 tons of molten iron at a temperature of 1415℃. The iron composition is: carbon 4.92%, silicon 0.40%, manganese 0.35%, and phosphorus 0.118%. The auxiliary material consumption for this furnace is: lime 2560 kg, limestone 1360 kg, raw dolomite 1330 kg, and dust collection ash briquettes 11600 kg.

[0058] The blowgun was initially positioned at 1630mm, and lowered to 1580mm after 1 minute and 30 seconds, with an oxygen supply intensity of 25100m. 3 / h; 9280kg of dust collector briquettes are added at 1 minute 35 seconds; 2048kg of lime, 1330kg of raw dolomite, and 680kg of limestone are added at 1 minute 40 seconds; the nozzle is lowered to 1530mm at 2 minutes, and the oxygen supply intensity is 26400m. 3 / h; Add 272kg of lime at 2 minutes and 30 seconds, lower the nozzle to 1480mm at 2 minutes and 40 seconds, lower the nozzle to 1430mm at 3 minutes, add 240kg of lime at 3 minutes and 20 seconds, lower the nozzle to 1380mm at 4 minutes, oxygen supply intensity 27800m 3 / h; 300kg limestone is added at 4 minutes 30 seconds, 230kg limestone at 5 minutes 45 seconds, 600kg dust collector briquettes at 6 minutes 10 seconds, 540kg dust collector briquettes at 6 minutes 55 seconds, 610kg dust collector briquettes at 7 minutes 50 seconds, 150kg limestone at 8 minutes 30 seconds, and 570kg dust collector briquettes at 9 minutes 30 seconds, with an oxygen supply intensity of 28000m. 3 / h; 10 minutes to lower the gun position to 1330mm, 10 minutes 30 seconds to 1280mm, 10 minutes 50 seconds to 1230mm, 11 minutes 10 seconds to 1180mm, oxygen supply intensity 26100m 3 / h.

[0059] Oxygen supply time was 719 seconds, the final temperature was 1612℃, and the final carbon content was 0.083% and phosphorus content was 0.023%.

[0060] Comparative Example 1

[0061] This comparative example uses the method described in patent document CN113528738A to produce steel grade Q235B. The molten iron produced was 139.8 tons at a temperature of 1403℃. The composition of the molten iron was: carbon 4.87%, silicon 0.35%, manganese 0.29%, and phosphorus 0.137%. The auxiliary material consumption for this furnace was: lime 5680 kg, raw dolomite 1980 kg, and ore 8530 kg.

[0062] The blow gun position is 1350mm, 4310kg of ore is added in 50 seconds, and the oxygen supply intensity is 23000m. 3 / h; after 1 minute and 30 seconds, raise the nozzle to 1580mm; after 1 minute and 50 seconds, add 3930kg of lime, 1978kg of raw dolomite, and 1430kg of ore; oxygen supply intensity 26000m. 3 / h; 3 minutes to raise the nozzle to 1620mm, 3 minutes 05 seconds to add 437kg of lime, 3 minutes 40 seconds to add 437kg of lime, 4 minutes 20 seconds to add 437kg of lime, 5 minutes to add 437kg of lime, oxygen supply intensity 25900m 3 / h; 5 minutes 05 seconds lower the lance to 1550mm, 5 minutes 50 seconds add 557kg of ore, 6 minutes 40 seconds add 557kg of ore, 7 minutes 20 seconds add 557kg of ore, 8 minutes 10 seconds add 557kg of ore, oxygen supply intensity 25900m 3 / h. The gun is lowered to the 1200mm position at the 13-minute mark, with an oxygen supply intensity of 26500m. 3 / h.

[0063] Oxygen supply time: 820 seconds; final temperature: 1648℃; final carbon content: 0.063%; phosphorus content: 0.035%.

[0064] Table 1 Unit Price of Each Material

[0065] Yuan / ton 765 98 123 265 1040

[0066] Table 2 Comparison of auxiliary material consumption and cost in Examples 1-5 and Comparative Example 1 Table 2 Comparison of auxiliary material consumption and cost in Examples 1-5 and Comparative Example 1

[0067]

[0068] Tables 1 and 2 show that, under high-temperature molten iron conditions, replacing part of the lime with limestone and using dust collector briquettes instead of sinter can effectively reduce auxiliary material costs. Furthermore, in all embodiments, no iron-laden splashing or yellow smoke occurred during the smelting process, and the final composition and temperature met the steel tapping control requirements. The control method in Comparative Example 1 is prone to poor slag formation in the early stages, iron-laden splashing causing smoke during the process, and high phosphorus levels at the final stage. Under high-temperature molten iron conditions, this invention achieves stable control of the converter smelting process by rationally adjusting the type and ratio of slag materials, optimizing the oxygen supply, temperature, and slag-forming systems, and utilizing the excellent cooling effect of limestone to balance the molten pool temperature.

Claims

1. A converter-based all-iron smelting process under high-temperature molten iron conditions, characterized in that, Includes the following steps: (1) After the slag splashing and furnace protection operation is completed, pour out all the slag and add all the molten iron; (2) Calculate the amount of bulk material to be added based on the iron conditions and the final control requirements of the steel grade. The bulk material includes lime, limestone, raw dolomite and dust removal ash briquettes. The iron temperature is 1370~1470℃. In step (2), the amount of lime added is calculated to be 16-19 kg / t steel, the amount of limestone added is 7-15 kg / t steel, and the amount of raw dolomite is 9-15 kg / t steel, based on the slag alkalinity requirements. In step (2), the total iron content of the dust collector briquettes is ≥50%, and the CaO content is 15~20%; In step (2), the endpoint control conditions for producing steel are: endpoint carbon 0.08-0.13%, endpoint temperature 1610-1640℃, and endpoint phosphorus content ≤0.030%. (3) Process smelting control; S1. Start blowing for 1 minute and 30 seconds, using a gun position of 1600-1650mm, and an oxygen supply intensity of 25000-26000m. 3 / h; S2. Oxygen supply for 1 minute 30 seconds to 2 minutes 30 seconds, using a gun position of 1450 to 1550 mm, and an oxygen supply intensity of 26,000 to 28,000 m³ / h. 3 Feeding begins at 1 minute 30 seconds to 1 minute 50 seconds per hour, during which lime (70-80% of total weight), limestone (40-50% of total weight), raw dolomite (all weight), and dust collector ash briquettes (70-80% of total weight) are added. In step S2, lime, limestone, raw dolomite, and dust removal ash briquettes are all added in one batch. S3. Oxygen supply for 2 minutes 30 seconds to 4 minutes, using a gun position of 1400mm to 1450mm, with an oxygen supply intensity of 27000 to 30000 m³ / h. 3 / h, during which the remaining 20-30% lime is added; In step S3, lime is added in 2 to 3 batches, with the amount of lime added in each batch controlled at 1 to 3 kg / t steel. S4. Oxygen supply of 4-10 minutes, using a gun position of 1200-1400mm, oxygen supply intensity of 28000-32000m. 3 / h, during which the remaining dust collection ash briquettes and limestone are added; In step S4, the remaining dust collector briquettes and limestone are added in batches. The amount of dust collector briquettes added in each batch is controlled at 2-5 kg / t steel, and the interval time is controlled at 50-70 s. The amount of limestone added in each batch is controlled at 1-3 kg / t steel, and the interval time is controlled at 1-3 min. S5. Oxygen supply for 10 minutes – end point: lift the nozzle, using a nozzle position of 1100–1200 mm and an oxygen supply flow rate of 26000–28000 m³ / h. 3 / h.

2. The converter all-iron smelting process under high-temperature molten iron conditions according to claim 1, characterized in that: The molten iron conditions mentioned in step (2) include molten iron composition, temperature and loading amount; the steel grade endpoint control requirements include endpoint carbon, endpoint temperature and endpoint phosphorus content.

3. The converter all-iron smelting process under high-temperature molten iron conditions according to claim 1 or 2, characterized in that: In step (2), the amount of molten iron charged is 130 to 145 tons; The composition of molten iron is: carbon 4.2-5.0%, silicon 0.25-0.55%, manganese 0.25-45%, and phosphorus 0.11-0.15%.

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