A method of converting steel

Abstract

The present application provides a converter steelmaking method. The converter steelmaking method provided by the present application controls different oxygen lance gun positions and blowing time in the early blowing, middle blowing and late blowing, and importantly, adds cut pellets in the blowing process. First, the cut pellets are added through the high-position stock bin when the slag is too active and is about to splash, so as to restore the normal slag and furnace mouth and prevent splashing. Second, the cut pellets are added through the uniform distribution bin in the process of blowing for 6min30s-8min30s, so as to balance the temperature of the molten pool and prevent the return-dry phenomenon in the blowing process. The method of the present application can solve the abnormal increase of the temperature of the molten pool, quickly adjust the temperature of the molten pool and reduce the occurrence of splashing furnace. Meanwhile, the cut pellets are used instead of part of the dust removal pressure ball in the present application, which can reduce the total slag amount of the converter and the consumption of steel materials. Moreover, the cut pellets are added in the blowing process of the present application, and the carbon-oxygen reaction is mainly in this stage. After the cut pellets are melted, the oxidation amount of manganese element is small, which can improve the residual manganese at the end point.

Description

Technical Field

[0001] This invention relates to the field of steelmaking, and in particular to a converter steelmaking method. Background Technology

[0002] The steelmaking process mainly includes the following steps: hot metal pretreatment → converter steelmaking → refining → continuous casting. The hot metal pretreatment step, conducted in the pretreatment workshop, primarily involves desulfurization, dephosphorization, and desiliconization of the hot metal. The converter steelmaking process uses pretreated hot metal, scrap steel, and slag-forming materials (primarily lime and ores such as dolomite) as main raw materials. It relies on the physical heat of the molten iron itself and the heat generated by the chemical reactions between the iron components to complete the steelmaking process in the converter without the aid of external energy. The refining step involves a series of processes to optimize the quality of the molten steel, including degassing, deoxidation, desulfurization, removal of inclusions, and fine-tuning of alloy composition. The continuous casting step involves feeding the refined molten steel into a continuous casting machine to form continuously cast billets.

[0003] In the aforementioned steelmaking process, the main tasks of the converter steelmaking process are decarburization, dephosphorization, and preliminary deoxidation and alloying. The actual implementation process of the converter steelmaking process mainly includes: charging → blowing → deoxidation and alloying → tapping → slag splashing for furnace protection and slag removal. Specifically, raw materials are charged into the converter, and then the oxygen lance is lowered to start blowing oxygen. The reaction heat of the raw materials themselves in the furnace will cause the furnace temperature to rise, and the reaction in the furnace is very intense, rapidly burning off carbon and major impurities (manganese and silicon in the molten iron are oxidized, and carbon in the molten iron is also oxidized into carbon dioxide and carbon monoxide). When the blowing endpoint is reached, the lance is raised and the furnace is drained, the temperature is measured, and samples are taken for composition analysis. If the temperature and composition of the molten steel meet the target, the steel is tapped; otherwise, the oxygen lance is lowered and blowing is repeated until it is qualified. During the tapping process, deoxidizers and ferroalloys are added for deoxidation and alloying, thereby obtaining converter steel. The entire process can produce a batch of steel without the addition of fuel.

[0004] However, during steelmaking, fluctuations occur in the converter smelting process due to factors such as employee operating skills, unstable raw material conditions, and equipment limitations. In some heats, splashing occurs due to inadequate temperature balance, posing challenges to process operation, flue gas slag accumulation, and equipment maintenance. Therefore, reducing splashing is crucial.

[0005] To address the aforementioned problems, existing technologies have proposed several solutions. For example, CN108977614 discloses a method for suppressing splashing in the early stage of converter smelting, which mainly reduces splashing by controlling the operation and conditions of lance lifting, charging, and depressurization. Another example is CN114150100, which discloses a converter steelmaking method that mainly improves steel quality and reduces splashing by controlling specific smelting modes in the early, middle, and late stages. However, these existing technologies either have complex process control or offer unsatisfactory improvement results. Summary of the Invention

[0006] In view of this, the present invention provides a converter steelmaking method that can effectively improve the splashing problem in converter smelting, reduce slag volume and steel consumption, and the method is simple and easy to implement.

[0007] This invention provides a converter steelmaking method, comprising the following steps:

[0008] A) Preliminary blowing: Add molten iron, scrap steel, the first batch of lime, raw dolomite and dust removal briquettes to the converter and start blowing. Control the oxygen lance position at 1.85m. When blowing for 3 min 30s to 4 min 10s, add the remaining lime.

[0009] B) Intermediate blowing: Lower the oxygen lance position to 1.45m to 1.50m and blow for 10 minutes and 30 seconds;

[0010] C) Later stage of blowing: Gradually lower the oxygen lance position to the final position, control the final lance pressing time to be no less than 30s, and the final lance position to be no higher than 1.10m;

[0011] During the blowing process in steps A) to C) above: control the oxygen pressure at 0.90–0.95 MPa and the oxygen flow rate at 30,000–35,000 Nm³. 3 / h; If abnormal slag activity or splashing occurs during the blowing process, add pellets to the converter; During the blowing process of 6min30s to 8min30s, add pellets to the converter again;

[0012] The pellets are obtained by cutting the edges of a steel plate or the ends of a rebar into pellets smaller than 5cm × 5cm.

[0013] Preferably, when abnormal slag activity or splashing occurs during the blowing process, the amount of chopped pellets added to the converter is 3 to 7.5 kg / t of steel.

[0014] Preferably, during the blowing process of 6 min 30 s to 8 min 30 s, the amount of chopped pellets added to the converter is 5 to 6.5 kg / t steel.

[0015] Preferably, when adding pellets to the converter again during the blowing process of 6 min 30 s to 8 min 30 s, the pellets are added in 2 to 4 batches, with an interval of 30 to 60 s between each batch, and the amount added in each batch is 300 to 500 kg.

[0016] Preferably, when abnormal slag activity or splashing occurs during the blowing process, pellets are added to the converter through a high-level silo;

[0017] The height of the elevated silo is 38.5m.

[0018] Preferably, during the blowing process of 6 min 30 s to 8 min 30 s, pellets are added back into the converter through a uniform distribution bin;

[0019] The height of the uniform fabric distribution bin is 38.5m.

[0020] Preferably, in step A), the temperature of the molten iron is ≥1400℃.

[0021] Preferably, in step A), the total amount of lime added is 80 times the silicon content of the molten iron.

[0022] Preferably, in step A), the amount of the first batch of lime added accounts for 70% to 80% of the total amount of lime.

[0023] Preferably, in step A), the silicon content of the molten iron is 0.25% to 0.50%.

[0024] The converter steelmaking method provided by this invention controls different oxygen lance positions and blowing times in the early, middle, and late blowing stages. Crucially, it incorporates pellets during the blowing process. Firstly, pellets are added from a high-level silo when the slag becomes overly active and splashing is imminent, restoring the slag and furnace opening to normal and preventing splashing. Secondly, pellets are added from a uniformly distributed silo during the blowing process from 6 min 30 s to 8 min 30 s, replacing part of the briquettes / sinter to balance the temperature and reducing the total slag volume in the converter. This method effectively addresses abnormally high molten pool temperatures, rapidly adjusting them and reducing the number of splashing furnace cycles. Furthermore, by using pellets to replace part of the dust-removing briquettes / sinter, the total slag volume in the converter is reduced, decreasing steel material consumption. Moreover, the addition of pellets during the blowing process, where the primary reaction is carbon-oxygen, results in less manganese oxidation after the pellets melt, thus increasing the residual manganese at the final stage. Detailed Implementation

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0026] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0027] As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0028] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0029] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 0.90~0.95MPa means that the units for the left endpoint "0.90" and the right endpoint "0.95" are both MPa.

[0030] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0031] This invention provides a converter steelmaking method, comprising the following steps:

[0032] A) Preliminary blowing: Add molten iron, scrap steel, the first batch of lime, raw dolomite and dust removal briquettes to the converter and start blowing. Control the oxygen lance position at 1.85m. When blowing for 3 min 30s to 4 min 10s, add the remaining lime.

[0033] B) Intermediate blowing: Lower the oxygen lance position to 1.45m to 1.50m and blow for 10 minutes and 30 seconds;

[0034] C) Later stage of blowing: Gradually lower the oxygen lance position to the final position, control the final lance pressing time to be no less than 30s, and the final lance position to be no higher than 1.10m;

[0035] During the blowing process in steps A) to C) above: control the oxygen pressure at 0.90–0.95 MPa and the oxygen flow rate at 30,000–35,000 Nm³. 3 / h; If abnormal slag activity or splashing occurs during the blowing process, add pellets to the converter; During the blowing process of 6min30s to 8min30s, add pellets to the converter again;

[0036] The pellets are obtained by cutting the edges of a steel plate or the ends of a rebar into pellets smaller than 5cm × 5cm.

[0037] The converter steelmaking method provided by the present invention includes a blowing process comprising early blowing, middle blowing and late blowing, as shown in steps A) to C) above.

[0038] Regarding step A) :

[0039] A) Initial blowing: Add molten iron, scrap steel, the first batch of lime, raw dolomite and dust removal briquettes to the converter and start blowing. Control the oxygen lance position at 1.85m. When blowing for 3 min 30s to 4 min 10s, add the remaining lime.

[0040] In this invention, the temperature of the molten iron is preferably ≥1400℃, more preferably 1400~1490℃, specifically 1400℃, 1410℃, 1420℃, 1430℃, 1440℃, 1450℃, 1459℃, 1460℃, 1470℃, 1480℃, and 1490℃. Generally, the amount of molten iron is 129~140 tons / furnace. In this invention, the amount of scrap steel added is preferably 15~36 tons / furnace, specifically 15 tons / furnace, 20 tons / furnace, 25 tons / furnace, 30 tons / furnace, 35.6 tons / furnace, and 36 tons / furnace. In this invention, the silicon content of the molten iron is preferably 0.25%~0.50%.

[0041] In this invention, the lime is added in batches. The first batch of lime is added initially, and the remaining lime is added after the initial blowing process has reached a certain stage. Preferably, the total amount of lime added is 80 times the silicon content of the molten iron. The first batch of lime accounts for 70% to 80% of the total lime amount, specifically 70%, 75%, or 80%.

[0042] In this invention, the preferred amount of raw dolomite added is 900-1600 kg / furnace, specifically 900 kg / furnace, 1000 kg / furnace, 1100 kg / furnace, 1200 kg / furnace, 1300 kg / furnace, 1400 kg / furnace, 1447 kg / furnace, 1500 kg / furnace, and 1600 kg / furnace.

[0043] In this invention, the dust collector briquettes are fine ash produced by dry dust removal in converters. Through the addition of adhesives, drying, and other processes, they are ultimately formed into small, oval-shaped briquettes. Their main component is iron, with a content ranging from 48% to 53%. There are no special restrictions on the type of adhesive used; any conventional adhesive in the field is acceptable. The dust collector briquettes have the functions of cooling and increasing iron oxide content in the slag. In this invention, the preferred dosage of the dust collector briquettes is 1500–8000 kg / furnace, specifically 1500 kg / furnace, 1925 kg / furnace, 2000 kg / furnace, 3000 kg / furnace, 4000 kg / furnace, 5000 kg / furnace, 6000 kg / furnace, 7000 kg / furnace, and 8000 kg / furnace.

[0044] In this invention, molten iron, scrap steel, the first batch of lime, raw dolomite, and dust removal briquettes are added to the converter before the blowing process begins. During this blowing process, the oxygen lance position is controlled at 1.85m. After blowing for 3 minutes 30 seconds to 4 minutes 10 seconds, the flame at the furnace mouth softens and small slag flakes are ejected. At this point, the remaining lime is added. The specific blowing times can be 3 minutes 30 seconds, 3 minutes 40 seconds, 3 minutes 50 seconds, 3 minutes 60 seconds, 4 minutes, or 4 minutes 10 seconds. In this invention, it is preferable to add the remaining lime in batches.

[0045] Regarding step B) :

[0046] B) Intermediate blowing: Lower the oxygen lance position to 1.45m to 1.50m and blow for 10 minutes and 30 seconds.

[0047] In this invention, after the initial blowing in step A), the oxygen lance position is lowered for further blowing, specifically to 1.45m to 1.50m, or more specifically, 1.45m or 1.50m. In this invention, the blowing time for this stage is 10 minutes and 30 seconds (calculated from the start of blowing in step A).

[0048] Regarding step C) :

[0049] C) Later stage of smelting: Gradually lower the oxygen lance position to the final position, control the final lance pressing time to be no less than 30s, and the final lance position to be no higher than 1.10m.

[0050] In this invention, after the intermediate blowing in step B), the oxygen lance position is gradually lowered to continue blowing, controlling the final lance position to be no higher than 1.10m. Furthermore, the final lance pressing time is controlled to be no less than 30s.

[0051] In this invention, during the blowing process in steps A) to C) above, the oxygen pressure is controlled to be 0.90–0.95 MPa, and the oxygen flow rate is controlled to be 30,000–35,000 Nm³. 3 / h. The oxygen pressure can specifically be 0.90 MPa, 0.91 MPa, 0.92 MPa, 0.93 MPa, 0.94 MPa, or 0.95 MPa. The oxygen flow rate can specifically be 30000 Nm³. 3 / h, 31000Nm 3 / h, 32000Nm 3 / h, 33000Nm 3 / h, 34000Nm 3 / h, 35000Nm 3 / h.

[0052] In this invention, pellets are added at different times during the blowing process in steps A) to C) above. The pellets are obtained by cutting the edges of steel plates or the ends of rebar into pellets smaller than 5cm × 5cm. This processing can be carried out using a shearing machine.

[0053] In this invention, during the blowing process of steps A) to C) above, the first addition of pellets occurs when abnormal slag activity or splashing occurs in the converter. In some embodiments of this invention, pellets are added at 5 min 20 s to 5 min 40 s when the slag becomes too active and splashing is imminent. The total amount of pellets added in this stage is preferably 3 to 7.5 kg / t of steel. In this invention, the pellets added in this stage can be added through a high-level silo, the height of which (i.e., the distance from the charging port to the furnace opening) is preferably 38.5 m. This stage of pellet addition allows the slag and furnace opening to return to normal, preventing splashing.

[0054] In this invention, during the blowing process of steps A) to C) above, the pellets are added again during the blowing process of 6 min 30 s to 8 min 30 s. The total amount of pellets added during this process is preferably 5 to 6.5 kg / t of steel. During this stage of feeding, it is preferable to add the pellets in batches, specifically 2 to 4 batches, with an interval of 30 to 60 s between each batch, and each batch containing 300 to 500 kg. In this invention, the pellets added in this stage can be added through a uniform distribution bin, the height of which (i.e., the distance from the feeding port to the furnace mouth) is preferably 38.5 m. The main purpose of adding pellets in this stage is to replace briquettes or sinter to balance the molten pool temperature and reduce the total amount of converter slag.

[0055] As can be seen, this invention adds pellets at two key moments during the blowing process. One is when the slag becomes overly active and splashing is imminent, pellets are added through a high-level silo to restore the slag and furnace opening to normal, preventing splashing. The other is during the blowing process from 6 minutes 30 seconds to 8 minutes 30 seconds, pellets are added through a uniform distribution silo to replace briquettes or sinter to balance the molten pool temperature and reduce the total slag volume in the converter. The cooling effect of 1 ton of pellets is 10.3℃ (1 ton of pellets is equivalent to the cooling effect of 400-500 kg of dust-removing briquettes). It can be seen that both of these pellet addition opportunities occur during the middle of the blowing process. Specifically, in this invention, pellets meeting the required size can be prepared in advance before blowing and transported by conveyor belts to the high-level silo and the uniform distribution silo for immediate use.

[0056] The converter steelmaking method provided by this invention controls different oxygen lance positions and blowing times in the early, middle, and late blowing stages. Crucially, it incorporates pellets during the blowing process. Firstly, pellets are added from a high-level silo when the slag becomes overly active and splashing is imminent, restoring the slag and furnace opening to normal and preventing splashing. Secondly, pellets are added from a uniformly distributed silo during the blowing process from 6 min 30 s to 8 min 30 s, replacing briquettes or sinter to balance the molten pool temperature and reduce the total slag volume in the converter. This method effectively addresses abnormally high molten pool temperatures, rapidly regulates them, and reduces the occurrence of splashing. Furthermore, by using pellets to replace part of the dust-removing briquettes / sinter, the total slag volume in the converter is reduced, decreasing steel material consumption. Moreover, the addition of pellets during the blowing process, where the primary reaction is carbon-oxygen, results in less manganese oxidation after the pellets melt, thus increasing the residual manganese at the final stage.

[0057] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0058] Example 1

[0059] Pre-processing: Cut the steel plate edges or the rebar ends into pellets smaller than 5cm x 5cm. Then, transport them by conveyor belt to a high-level silo (38.5m high) and a uniform distribution silo (38.5m high) for later use.

[0060] A) Initial blowing: Add 130.8 tons of molten iron (temperature 1459℃) (containing 0.42% silicon), 35.6 tons of scrap steel, 2300 kg of the first batch of lime, 1447 kg of raw dolomite, and 1925 kg of dust removal briquettes to the converter and start blowing. Control the oxygen lance position at 1.85m. When blowing for 3 minutes and 50 seconds, the flame at the furnace mouth softens and small slag flakes are thrown out from the furnace mouth. At this time, add the remaining 826 kg of lime.

[0061] B) Intermediate blowing: Lower the oxygen lance position to 1.45m and blow for 10 minutes and 30 seconds. At 5 minutes and 20 seconds, the slag became too active and splashing was imminent. At this point, 526 kg of pellets from the high-level charging hopper was added to the converter. After 30 seconds, the slag and furnace flame returned to normal, and splashing did not occur. During the blowing process from 6 minutes and 30 seconds to 8 minutes and 30 seconds, 1000 kg of pellets were added evenly through the charging hopper, in two batches (60 seconds apart), with 500 kg added in each batch.

[0062] C) Later stage of blowing: After 10 minutes and 30 seconds, gradually lower the blowing gun position to 1.10m to ensure that the final pressing time is not less than 30 seconds. This stage takes a total of 2 minutes and 8 seconds.

[0063] During steps A) to C) above, the oxygen pressure is controlled at 0.92 MPa, and the oxygen flow rate can be specifically 33000 Nm³. 3 / h.

[0064] The final TSO temperature of this furnace blowing operation was 1650℃, and the sample contained 0.101% carbon, 0.256% residual manganese, and 0.026% phosphorus.

[0065] Comparative Example 1

[0066] A) Initial blowing: Add 128.6 tons of molten iron (temperature 1446℃) (containing 0.38% silicon), 36.4 tons of scrap steel, 2100 kg of the first batch of lime, 1247 kg of raw dolomite, and 1325 kg of dust removal briquettes to the converter and start blowing. Control the oxygen lance position at 1.85 m. When blowing for 4 minutes and 10 seconds, the flame at the furnace mouth softens and small slag flakes are thrown out from the furnace mouth. At this time, add the remaining 760 kg of lime.

[0067] B) Intermediate blowing: Lower the oxygen lance position to 1.45m and blow for 10 minutes and 30 seconds. At 5 minutes and 40 seconds, if the slag becomes too active and splashing is about to occur, immediately add two batches of dolomite to the converter (30 seconds apart), each batch weighing 300 kg, until the slag overflows from the furnace opening. After blowing for 7 minutes, add a batch of dust removal briquettes every minute, for a total of 3 batches, totaling 1500 kg.

[0068] C) Later stage of blowing: After 10 minutes and 30 seconds, gradually lower the blowing gun position to 1.10m to ensure that the final pressing time is not less than 30 seconds. This stage takes a total of 2 minutes and 18 seconds.

[0069] During steps A) to C) above, the oxygen pressure is controlled at 0.92 MPa, and the oxygen flow rate can be specifically 33000 Nm³. 3 / h.

[0070] The TSO temperature at the end of this furnace blowing process was 1643℃, and the sample contained 0.092% carbon, 0.225% residual manganese, and 0.031% phosphorus.

[0071] During the tapping of this heat, the slag inside the furnace was observed to be sticky. After tapping, oxygen was blown into the tapping port to modify the slag and prevent the sticky slag from sintering on the furnace bottom, which would cause the furnace bottom to rise abnormally.

[0072] Comparative Example 2

[0073] A) Initial blowing: Add 130.4 tons of molten iron (temperature 1410℃) (containing 0.48% silicon), 32.9 tons of scrap steel, 2700 kg of the first batch of lime, 1547 kg of raw dolomite, and 1750 kg of dust removal briquettes to the converter and start blowing. Control the oxygen lance position at 1.85m. When blowing for 4 minutes and 22 seconds, the flame at the furnace mouth softens and small slag flakes are thrown out from the furnace mouth.

[0074] B) Intermediate blowing: Lower the oxygen lance position to 1.45m and blow for 10 minutes and 30 seconds. At 4 minutes and 36 seconds, the slag became too active and splashing was imminent. Immediately, three batches of lime (300 kg each, 30 seconds apart) were added to the converter, but splashing still occurred. After 7 minutes of blowing, a batch of dust removal briquettes was added every minute, for a total of four batches, totaling 1600 kg.

[0075] C) Later stage of blowing: After 10 minutes and 30 seconds, gradually lower the blowing gun position to 1.10m to ensure that the final pressing time is not less than 30 seconds. This stage takes a total of 2 minutes and 41 seconds.

[0076] During steps A) to C) above, the oxygen pressure is controlled at 0.92 MPa, and the oxygen flow rate can be specifically 33000 Nm³. 3 / h.

[0077] The TSO temperature at the end of this heat was 1647℃. The sample contained 0.082% carbon, 0.231% residual manganese, and 0.020% phosphorus. During tapping, the slag was foamy. The converter was shaken to zero, and nitrogen was used to purge the slag.

[0078] As can be seen from Example 1 and Comparative Examples 1-2 above, the present invention introduces pelletizing into the blowing process, which can effectively reduce splashing, increase the residual manganese content at the end point, and reduce slag.

[0079] The experiment revealed the following effects achieved by the present invention:

[0080] 1. The present invention adds granulated material during the blowing process, which can quickly reduce the temperature of the molten pool when the temperature rises sharply, thereby reducing the occurrence of splashing phenomenon. The splashed slag is reduced from 12.6 kg / t steel to 9.3 kg / t steel, a reduction of 3.3 kg / t steel.

[0081] 2. This invention uses pellets to replace part of the dust removal briquettes, which can reduce the total slag volume and steel material consumption in the converter. See Table 1 for details:

[0082] Table 1: Effects of replacing part of the dust collection briquettes with pelletized pellets

[0083] Pelletizing amount, kg Replacement briquetting amount, kg Reduce slag volume, kg / t Reduce steel material costs, yuan / t 1000 500 1.64 0.73 2000 1000 3.29 1.47 3000 1500 4.93 2.20 4000 2000 6.58 2.93

[0084] The calculation for reducing steel costs is: reduction in slag volume × iron content in slag × steel price. The iron content in slag is calculated as 15%, and the steel price is 2973 yuan / ton.

[0085] 3. In this invention, pellets are added during the blowing process. At this stage, the main reaction is carbon-oxygen reaction. After the pellets melt, the amount of manganese element oxidized is small, which has the effect of increasing the residual manganese at the end point. The residual manganese content at the end point increases from 0.217% to 0.224%, and the average residual manganese content increases by 0.007%. After the residual manganese content of the molten steel is increased, the amount of alloy added can be reduced, which can reduce the production cost. The reduction of alloy cost = increase in residual manganese content / manganese content of silicon-manganese alloy / manganese element recovery rate * price of silicon-manganese alloy = 0.007% / 65% / 92% × 6239 = 0.73 yuan / ton of steel. Notes: (1) The amount of residual manganese is increased by 0.007%; (2) The manganese element content of silicon-manganese alloy is 65%; (3) The manganese element alloy recovery rate is 92%; (4) The price of silicon-manganese alloy is 6239 yuan / ton.

[0086] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A converter steelmaking method, characterized in that, Includes the following steps: A) Preliminary blowing: Add molten iron, scrap steel, the first batch of lime, raw dolomite and dust removal briquettes to the converter and start blowing. Control the oxygen lance position at 1.85m. When blowing for 3 minutes 30 seconds to 4 minutes 10 seconds, add the remaining lime. B) Intermediate blowing: Lower the oxygen lance position to 1.45m~1.50m and blow for 10min30s; C) Later stage of blowing: Gradually lower the oxygen lance position to the final position, control the final lance pressing time to be no less than 30s, and the final lance position to be no higher than 1.10m; During the blowing process in steps A) to C) above: control the oxygen pressure at 0.90~0.95MPa and the oxygen flow rate at 30000~35000Nm. 3 / h; If abnormal slag activity or splashing occurs during the blowing process, add pellets to the converter; During the blowing process of 6min30s~8min30s, add pellets to the converter again; The pellets are obtained by cutting the edges of a steel plate or the ends of a rebar into pellets smaller than 5cm × 5cm. When abnormal slag activity or splashing occurs during the blowing process, the amount of chopped slag added to the converter is 3~7.5 kg / t steel; During the blowing process of 6 min 30 s to 8 min 30 s, the amount of chopped pellets added to the converter is 5 to 6.5 kg / t of steel.

2. The converter steelmaking method according to claim 1, characterized in that, During the blowing process of 6min30s~8min30s, when adding pellets to the converter again, add them in 2~4 batches, with an interval of 30~60s between each batch, and the amount added in each batch is 300~500kg.

3. The converter steelmaking method according to claim 1, characterized in that, If abnormal slag activity or splashing occurs during the blowing process, pellets are added to the converter through the high-level silo. The height of the elevated silo is 38.5m.

4. The converter steelmaking method according to claim 1, characterized in that, During the blowing process of 6 min 30 s to 8 min 30 s, pellets are added back into the converter through the uniform material distribution bin; The height of the uniform fabric distribution bin is 38.5m.

5. The converter steelmaking method according to claim 1, characterized in that, In step A), the temperature of the molten iron is ≥1400℃.

6. The converter steelmaking method according to claim 1, characterized in that, In step A), the total amount of lime added is 80 times the silicon content of the molten iron.

7. The converter steelmaking method according to claim 1 or 6, characterized in that, In step A), the amount of lime added in the first batch accounts for 70% to 80% of the total amount of lime.

8. The converter steelmaking method according to claim 1 or 6, characterized in that, In step A), the silicon content of the molten iron is 0.25% to 0.50%.