A method for producing high-nitrogen steel

Abstract

This application relates to a method for producing high-nitrogen steel, belonging to the steelmaking field, which includes blowing N2 into a ladle, wherein the N2 flow rate during the tapping stage is 1000-1500 m³ / h. 3 / h; N2 flow rate during the inlet-sampling stage: 800~1200m³ / h 3 / h; N2 flow rate during the isostatic stage: 100~300m³ / h 3 / h; N2 flow rate during the make-up blow-departure phase: 200~600m³ / h 3 / h. This application achieves the effect of obtaining steel with a stable nitrogen content by controlling the flow rate of nitrogen gas in the ladle.

Description

Technical Field

[0001] This application relates to the field of steelmaking, and in particular to a method for producing high-nitrogen steel. Background Technology

[0002] The nitrogen content range, bottom-blown nitrogen pressure, and flow rate process parameters in the existing HRB500E rebar chromium smelting process are all publicly available.

[0003] Nitrogen addition to steel is usually achieved by adding nitride alloys to the molten steel. The most common method is to use nitrogen-enhancing alloys to increase the nitrogen content in the steel.

[0004] The existing process scheme lacks information on how nitrogen is obtained from steel and the process control measures adopted to ensure that the nitrogen content in steel is within the target range. Summary of the Invention

[0005] This application provides a method for producing high-nitrogen steel, which achieves stability.

[0006] This application provides a method for producing high-nitrogen steel, including blowing N2 into a ladle, wherein the N2 flow rate during the tapping stage is 1000-1500 m³ / h. 3 / h; N2 flow rate during the inlet-sampling stage: 800~1200m³ / h 3 / h; N2 flow rate during the isostatic stage: 100~300m³ / h 3 / h; N2 flow rate during the make-up blow-off phase: 200~600m³ / h 3 / h.

[0007] Furthermore, it also includes tapping, which involves pouring molten steel from the tapping port of the converter into a ladle; after tapping begins, a nitrogen-containing alloy is added to the ladle after n seconds, with the addition time of the nitrogen-containing alloy being m seconds; wherein, as the number of furnaces used by the tapping port increases, n gradually decreases to a set value and then remains constant, and m gradually decreases to a set value and then remains constant.

[0008] Furthermore, it also includes a converter smelting process; in the converter smelting process, N2 is continuously blown into the bottom of the converter.

[0009] Furthermore, the converter smelting process includes slag splashing, ferroalling, blowing, secondary lance sampling, spot blowing, manual sampling, equal sampling, and tapping stages; wherein, the flow rate of N2 introduced during the slag splashing stage is approximately 800 m³ / s. 3 / h; the flow rate of N2 introduced during the iron mixing stage is approximately 360m³ / h. 3 / h; the flow rate of N2 introduced during the blowing stage is 280-420m³ / h. 3 / h; The flow rate of N2 introduced during the secondary gun sampling stage is 200-300m³ / h. 3 / h; the flow rate of N2 introduced during the spritz stage is 280-420 m³ / h. 3 / h; the flow rate of N2 introduced during the manual sampling stage is 200-300 m³ / h. 3 / h; the flow rate of N2 introduced during the isosample stage is 200-300 m³ / h. 3 / h; the flow rate of N2 introduced during the tapping stage is 200-300 m³ / h. 3 / h.

[0010] In the above technical solution, nitrogen is blown into the ladle, and the nitrogen flow rate is controlled during the steel tapping, station entry, sample waiting, and supplementary blowing stages, so as to obtain steel with nitrogen content at the target content and stabilize the nitrogen content qualification rate.

[0011] It reduces production costs. Compared to bottom-blown argon, bottom-blown nitrogen is cheaper. Bottom-blown nitrogen increases the nitrogen content in the steel, thereby reducing the amount of nitrogen-containing alloys used and lowering production costs.

[0012] By controlling the timing of adding nitrogen-containing alloys to the ladle, the yield of nitrogen-containing alloys was improved, further reducing production costs. Detailed Implementation

[0013] The present application will be further described in detail below through embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0014] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0015] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0016] This application discloses a method for producing high-nitrogen steel. The production process of high-nitrogen steel includes converter smelting, converter tapping to ladle, and ladle nitrogen blowing. This embodiment describes the three stages of converter smelting, converter tapping to ladle, and ladle nitrogen blowing in sequence. Before the ladle nitrogen blowing stage, the method described in this embodiment for the converter tapping to ladle stage can be selected according to process requirements; before the converter tapping to ladle stage, the method described in this embodiment for the converter smelting stage can be selected according to process requirements.

[0017] In this embodiment, nitrogen gas with different flow rates is blown into the bottom at different stages of converter smelting to increase the nitrogen content in the steel. During the stage from converter tapping to ladle, the timing and rate of adding nitrogen-containing alloys to the ladle are controlled to stably increase the nitrogen content in the steel. During the ladle nitrogen blowing stage, a stable high-nitrogen steel content is obtained by adjusting the flow rate of nitrogen gas blown into the ladle.

[0018] The converter used in this embodiment has a capacity of 80-150t, an N2 pressure ≥1.2MPa, and an N2 purity ≥99.99%. The following example illustrates the production process of high-nitrogen, earthquake-resistant rebar HRB500E, where HRB500E is the grade.

[0019] I. Converter Smelting Stage

[0020] Nitrogen is supplied via bottom blowing; the nitrogen flow rate control in different processes is shown in the table below:

[0021]

[0022] The nitrogen flow rate for the slag splashing process is 800 m³ / h. 3 / h and nitrogen flow rate during the iron mixing stage: 360m 3 / h represents the general flow rate requirement. In the actual smelting stage, those skilled in the art are allowed to adjust it upwards or downwards according to actual needs.

[0023] Nitrogen flow rate during the blowing process is 280–420 m³ / h. 3 Between / h, the maximum actual nitrogen flow rate during the blowing period can be slightly greater than 420 and the minimum can be slightly less than 280. The endpoint values ​​for the secondary lance sampling, spot blowing, manual sampling, equal sampling, and steel tapping processes can all be slightly greater than the maximum value and slightly less than the minimum value.

[0024] It should be noted that in this embodiment, ~ includes endpoint values, such as 280~420m. 3 / h indicates that the endpoint values ​​can be 280 and 420.

[0025] As an optional solution, the nitrogen flow control in different processes is shown in the table below:

[0026]

[0027] Further restrictions on the nitrogen flow rate range during the blowing period, secondary lance sampling, spot blowing, manual sampling, waiting for samples, and steel tapping processes can yield molten steel with a higher nitrogen content.

[0028] Compared to existing converters that use a combination of top and bottom blowing, with argon blowing at the bottom, this patent uses nitrogen blowing at the bottom. This reduces the use of argon, as nitrogen is typically 5-8% the price of argon, thus lowering costs.

[0029] Controlling nitrogen flow rate in different processes can stabilize the nitrogen content in steel, while bottom-blown nitrogen increases the nitrogen content. Through nearly a thousand heats of trials and production implementation, the bottom-blown nitrogen process in converters can increase the nitrogen content of high-nitrogen rebar HRB500E by 8-13%.

[0030] By using nitrogen blowing from the bottom of the converter, the nitrogen content of the molten steel is increased during tapping, reducing production costs and increasing efficiency.

[0031] It should be noted that m in this embodiment 3 / h refers to standard cubic meters per hour, where the air conditions are: one standard atmosphere, temperature of 0°C, and relative humidity of 0%.

[0032] II. From converter tapping to ladle stage

[0033] When tapping steel from the converter, deoxidizer, slag-forming agent, carbon powder, and deoxidizing alloy are added first. Nitrogen-containing alloy is added 60 seconds or more after tapping.

[0034] Nitrogen-containing alloys include at least one of vanadium-nitrogen alloys, high-nitrogen ferrovanadium, manganese nitride, and chromium nitride.

[0035] Tapping refers to the process of pouring molten steel from the tapping port of the converter into the ladle.

[0036] After tapping begins, n seconds later, a nitrogen-containing alloy is added to the ladle. The addition time for the nitrogen-containing alloy is m seconds.

[0037] As the number of furnaces using the tapping outlet increases, n gradually decreases to a set value and then remains constant, while m gradually decreases to a set value and then remains constant.

[0038] The nitrogen-containing alloy is added in m seconds, which means that the nitrogen-containing alloy needs to be uniformly added to the ladle within m seconds.

[0039] As an optional approach, the following explanation is provided regarding the timing of adding the nitrogen-containing alloy (n seconds) and the timing of adding the nitrogen-containing alloy (m seconds), based on the heat number used at the tapping outlet:

[0040] The tapping outlet is used for 1 to 20 heats, n is 80 to 150, and m is 120 to 150.

[0041] The tapping outlet is used for 21 to 50 heats, n is 70 to 79, and m ranges from 90 to 120;

[0042] The tapping outlet is used for 51 to 130 heats, n is 60 to 69, and m is 60 to 90.

[0043] The tapping outlet is used for more than 130 heats, n is less than 60, and m ranges from 30 to 60.

[0044] Nitrogen-containing alloys are generally added bag by bag sequentially, with the rate of addition of each bag of nitrogen-containing alloy to the ladle being as uniform as possible. Typically, 5 kg of vanadium-nitrogen alloy is added per bag. When the steel tapping station is used for more than 130 heats, it is advisable to have 1 to 2 people simultaneously handling the nitrogen-containing alloy operation.

[0045] The tapping outlet is used for 1 to 20 heats, with n ranging from 80 to 150 and m ranging from 120 to 150. This indicates that when the tapping outlet is used for 1, 2, 3...19 or 20 heats, the nitrogen-containing alloy is first added 80 to 150 seconds after the start of tapping, and the time for uniformly adding the nitrogen-containing alloy into the ladle is controlled between 120 and 150 seconds. It should be noted that the value of n (90) is allowed to have a slight deviation; for example, n can be 88, 89, 91, or 92. The time for adding the nitrogen-containing alloy into the ladle is allowed to be slightly less than 120 seconds or slightly more than 150 seconds.

[0046] When the steel tapping outlet is used for heats 21, 22, 23...49 or 50, the nitrogen-containing alloy should be added 70 to 79 seconds after the steel tapping begins, and the time for uniformly adding the nitrogen-containing alloy into the ladle should be controlled between 90 and 120 seconds.

[0047] When the steel tapping outlet is used for heats 51, 52, 53...129 or 130, the nitrogen-containing alloy should be added 60 to 69 seconds after the steel tapping begins, and the time for uniformly adding the nitrogen-containing alloy into the ladle should be controlled between 60 and 90 seconds.

[0048] When the tapping station is used for heats 131 or 132 and above until the tapping station is scrapped, the time for adding the nitrogen-containing alloy should not exceed 60 seconds from the start of tapping. The time for uniformly adding the nitrogen-containing alloy into the ladle should be controlled between 30 and 60 seconds. It should be noted that the value of n here is close to 60. The time for adding the nitrogen-containing alloy into the ladle is allowed to be slightly less than 60 seconds or slightly more than 90 seconds.

[0049] As an optional option, the tapping spout is used for 130 heats or more, with m ranging from 42 to 60. When the tapping spout is used for 131 or 132 heats or more until the tapping spout is scrapped, the nitrogen-containing alloy is added starting approximately 60 seconds after the tapping begins, and the time for uniformly adding the nitrogen-containing alloy into the ladle is controlled between 42 and 60 seconds.

[0050] When adding nitrogen-containing alloys to a ladle, the longer the addition time m, the more uniform the addition of the nitrogen-containing alloys into the ladle when adding the same amount of nitrogen-containing alloys, which helps to improve the utilization rate of nitrogen-containing alloys.

[0051] The timing of adding nitrogen-containing alloys to molten steel during converter tapping affects steel quality. Adding the alloy too early results in partial oxidation due to the strong oxidizing properties of the steel; adding it too late disrupts converter tapping operations. The service life of the converter tapping spout is generally 280–320 heats, with a tapping time of 2.5–5.5 minutes. There is an inverse relationship between the number of heats tapped and the tapping time: newly tapped spouts are less eroded by the steel flow, resulting in a smaller flow and longer tapping time; later tapping spouts have a larger flow and shorter tapping time.

[0052] In existing technologies, nitrogen-containing alloys are added immediately after the deoxidizing alloy is added during steel tapping, or it is specified that nitrogen-containing alloys should be added 1 to 1.5 minutes after tapping. Operators will add the nitrogen-containing alloy as quickly as possible, resulting in large fluctuations in the nitrogen recovery rate in the steel. Under normal circumstances, the nitrogen recovery rate is 65 to 80%, and the nitrogen content in the steel is unstable.

[0053] In this embodiment, the furnace age at the tapping point is divided into four stages. The timing of adding nitrogen-containing alloys and the time after adding nitrogen-containing alloys are determined according to different furnace ages, thereby improving the nitrogen recovery rate. According to this scheme, the nitrogen recovery rate of steel is between 78% and 85%, and the nitrogen content in the steel is stable.

[0054] It should be noted that during the converter smelting stage, the amount of nitrogen in the steel is increased, which reduces the amount of nitrogen-containing alloys added to the ladle, thus also reducing costs.

[0055] III. Ladle Nitrogen Blowing Stage

[0056] N2 is blown into the ladle, with the N2 flow rate during the tapping stage being 1000–1500 m³ / h. 3 / h;

[0057] N2 flow rate during the inlet-sampling stage: 800-1200 m³ / h 3 / h;

[0058] N2 flow rate during the isostatic stage: 100–300 m³ 3 / h;

[0059] N2 flow rate during the make-up blow-off phase: 200-600 m³ / h 3 / h.

[0060] During the tapping stage, a large flow of nitrogen gas is blown into the ladle, and the turbulence of the molten steel causes the nitrogen-containing alloy to be encapsulated within the molten steel.

[0061] During the sampling phase, 800–1200 m³ / h is used. 3 A flow rate of nitrogen per hour keeps the molten steel agitated, and a sample is taken from the ladle at this time.

[0062] During the sample preparation stage, the molten steel maintains slight fluctuations to stabilize the nitrogen content in the steel.

[0063] During the supplementary blowing-off stage, based on the nitrogen content results of the ladle samples, nitrogen is added again to bring the nitrogen content of the finished molten steel into the acceptable range. After a period of supplementary blowing, another sample of the molten steel is taken as two ladle samples.

[0064] In existing technologies, the pass rate for nitrogen content in steel fluctuates greatly, ranging from 57% to 92%, with an average pass rate of 72.14%.

[0065] After adopting the method described in this embodiment, data from thousands of trial productions show that the nitrogen qualification rate of HRB500E steel ranges from 83% to 96.5%, with an average of 91.62%, an improvement of nearly 20%.

[0066] This results in high-nitrogen steel with high stability, where the nitrogen content is between 160 and 220 ppm (parts per million).

[0067] In existing technologies, molten steel in continuous casting requires ladle agitation to ensure stable and uniform steel temperature during pouring. Agitation is a necessary technical measure to guarantee the quality of continuously cast steel. The purposes of ladle agitation include: homogenizing steel temperature, homogenizing steel composition, and promoting the collision and floating of inclusions.

[0068] In this embodiment, when nitrogen is used to blow and stir the ladle at different stages and with different flow rates, not only can the effects of the prior art be achieved, but also high-nitrogen steel with high stability can be obtained.

[0069] As an optional approach, during the make-up blow-off stage, the nitrogen content of the ladle samples is controlled by the following N2 flow rate:

[0070] When the nitrogen content of the ladle sample meets the target nitrogen content, the N2 flow rate during the make-up blow-off stage is 200-300 m³ / h. 3 / h defines the nitrogen flow rate at this point as the low flow rate.

[0071] When the nitrogen content in the ladle sample is less than the target nitrogen content, such as 140–159 ppm; the N2 flow rate during the make-up blow-off stage is 301–400 m³ / h. 3 / h is defined as the medium flow rate of nitrogen gas at this point.

[0072] When the nitrogen content in the ladle sample is much lower than the target nitrogen content, such as less than 140 ppm, a high-flow-rate make-up blowing method should be used. The N2 flow rate during the make-up blowing-off stage is 401-600 m³ / h. 3 / h is defined as the medium flow rate of nitrogen gas at this point.

[0073] The difference between the nitrogen content in the ladle sample and the target nitrogen content of 160–220 ppm is positively correlated. The larger the difference between the nitrogen content in the ladle sample and the target nitrogen content of 160–220 ppm, the greater the N2 flow rate during the make-up blow-off stage, and the closer it is to 600 m³ / s.3 / h. The smaller the difference between the nitrogen content in the ladle sample and the target nitrogen content of 160–220 ppm, the smaller the N2 flow rate during the make-up blow-off stage, and the closer it is to 300 m³ / h. 3 / h.

[0074] Based on the nitrogen content results of the ladle samples, it was determined that large, medium, and small flow rates of N2 should be used for supplemental blowing to predict that the nitrogen content of the finished molten steel would be within the acceptable range. When the nitrogen content in the ladle samples met the target nitrogen content, a small flow rate of N2 was used for supplemental blowing. The N2 flow rate during the supplemental blowing-off stage was 200–300 m³ / h. 3 / h;

[0075] Specifically, when the nitrogen content of the ladle sample is 140–159 ppm, a medium-flow make-up blowing is used, with the N2 flow rate during the make-up blowing-off stage being 301–400 m³ / h. 3 / h.

[0076] When the nitrogen content in the ladle sample is less than 140 ppm, a high-flow-rate make-up purging is used. N2 flow rate during the make-up purging-departure phase: 401–600 m³ / h. 3 / h.

[0077] It should be noted that the standard for rebar (GB / T1499.2-2018, "Steel for Reinforced Concrete") clearly stipulates the nitrogen (N) content: "7.2.3 The nitrogen content of the steel should not exceed 0.012%. If the supplier can guarantee this, analysis is not required. If the steel contains a sufficient amount of nitrogen-binding elements, the nitrogen content limit can be appropriately relaxed." In other words, by adding nitrogen-binding elements such as V, Ni, and Ti, the nitrogen content of the steel can exceed 0.012%. Although the high-nitrogen rebar in this embodiment has a nitrogen content greater than 0.012%, it still meets the standard for rebar.

[0078] Example 1

[0079] Smelting in a 120t converter with a steel output of approximately 125t, the cross-sectional dimensions of the continuously cast billet are: 165×165mm;

[0080] 1) Nitrogen (N2) is blown into the bottom throughout the converter smelting process. N2 pressure: 1.32 MPa, N2 purity: 99.995%.

[0081] 2) The bottom-blown N2 flow rate control at each stage of smelting is shown in the table below:

[0082]

[0083] 3) During converter tapping, [C]: 0.08%, temperature: 1672℃, tapping port (number of furnaces): 16, tapping time: 5 min 25 s. Deoxidizer, slagging agent, carbon powder, deoxidizing alloy, etc., were added according to the operating procedures. The tapped steel sample [N]: 47 ppm. Data from this furnace shows that using the original process, the converter bottom-blown argon tapped steel sample [N]: 28 ppm. In this embodiment, the nitrogen content increased by: [N]: 47 - 28 = 19 ppm. It should be noted that in this embodiment, [C] represents the carbon content, and [N] represents the nitrogen content.

[0084] It should be noted that the original process involved bottom-blowing nitrogen, adding a nitrogen-containing alloy during tapping, and blowing nitrogen into the ladle to stir the molten steel.

[0085] 4) According to the steel tapping port, use 16 heats. Start adding 105 kg of nitrogen-containing alloy evenly bag by bag 1.5 min after tapping, and finish adding it in 2 min 36 s.

[0086] 5) Ladle N2 blowing operation: ① N2 blowing flow rate during tapping stage: 1200 m³ / h 3 / h; ② During the inlet-sampling stage, one sample from the ladle [N]: 157ppm, nitrogen yield: 84.4%, N2 blowing flow rate: 1000m 3 / h; ③ Isostatic stage, N2 flow rate: 120m³ / h; 3 / h; ④ During the supplementary blowing-off stage, two samples from the ladle [N]: 176ppm, blowing N2 flow rate: 500m³ / h. 3 / h.

[0087] 6) Ladle temperature at station: 1561℃, tundish finished product sample [N]: 193ppm.

[0088] The contribution of bottom-blown N2 in the converter [N]: 19 / (193-28)=0.114=11.4%.

[0089] Example 2:

[0090] Smelted in an 80t converter with a steel output of approximately 95t, the cross-sectional dimensions of the continuously cast billet are 165×165mm.

[0091] 1) Nitrogen (N2) is blown into the bottom throughout the converter smelting process. N2 pressure: 1.22 MPa, N2 purity: 99.995%.

[0092] 2) The bottom-blown N2 flow rate control at each stage of smelting is shown in the table below:

[0093]

[0094] 3) During converter tapping, [C]: 0.14%, temperature: 1663℃, tapping port (number of furnaces): 261, tapping time: 2 min 43 s. Deoxidizer, slagging agent, carbon powder, deoxidizing alloy, etc., were added according to the operating procedures. The tapped steel sample [N]: 38 ppm. Data from this furnace shows that using the original process, the converter bottom-blown argon gas tapped steel sample [N]: 24 ppm. In this embodiment, the nitrogen content increased by: [N]: 38 - 24 = 14 ppm.

[0095] 4) According to the 261 heats used at the tapping port, start adding 85kg of nitrogen-containing alloy bag by bag evenly 1 minute after tapping, and finish adding it in 51 seconds.

[0096] 5) Ladle N2 blowing operation: ① N2 blowing flow rate during tapping stage: 1300 m³ / h 3 / h; ② During the inlet-sampling stage, one sample from the ladle [N]: 175ppm, nitrogen yield: 82.7%, N2 blowing flow rate: 1100m 3 / h; ③ Isostatic stage, N2 flow rate: 100m³ / h 3 / h; ④ During the supplementary blowing-off stage, two samples from the ladle [N]: 182ppm, blowing N2 flow rate: 200m³ / h; 3 / h.

[0097] 6) Ladle temperature at station: 1567℃, tundish finished product sample [N]: 197ppm.

[0098] The contribution of bottom-blown N2 in the converter [N]: 14 / (197-24)=0.081=8.1%.

[0099] Example 3:

[0100] Smelting in a 150t converter, with a steel output of approximately 178.6t, the cross-sectional dimensions of the continuously cast billet are 165×165mm;

[0101] 1) Nitrogen (N2) is blown into the bottom throughout the converter smelting process. N2 pressure: 1.37 MPa, N2 purity: 99.995%.

[0102] 2) The bottom-blown N2 flow rate control at each stage of smelting is shown in the table below:

[0103]

[0104] 3) During converter tapping, [C]: 0.105%, temperature: 1683℃, tapping port (number of furnaces): 89, tapping time: 3 min 44 s. Deoxidizer, slagging agent, carbon powder, deoxidizing alloy, etc., were added according to the operating procedures. The tapped steel sample [N]: 59 ppm. Data from this furnace shows that using the original process, the converter bottom-blown argon gas tapped steel sample [N]: 30 ppm. In this embodiment, the nitrogen content increased by: [N]: 54 - 30 = 24 ppm.

[0105] 4) According to the steel tapping port, for 89 heats, start adding 155kg of nitrogen-containing alloy bag by bag evenly 1 minute after tapping, and finish adding it in 1 minute and 23 seconds.

[0106] 5) Ladle N2 blowing operation: ① N2 blowing flow rate during tapping stage: 1500m³ 3 / h; ② During the inlet-sampling stage, one sample from the ladle [N]: 192ppm, nitrogen yield: 85%, N2 blowing flow rate: 1200m 3 / h; ③ Isostatic stage, N2 flow rate: 300m³ / h 3 / h; ④ During the supplementary blowing-off stage, two samples from the ladle [N]: 201ppm, blowing N2 flow rate: 500m 3 / h.

[0107] 6) Ladle temperature at station: 1575℃, tundish finished product sample [N]: 217ppm.

[0108] The contribution of bottom-blown N2 in the converter [N]: 24 / (217-30) = 0.128 = 12.8%.

[0109] Example 4:

[0110] Smelting in a 100t converter with a steel output of approximately 115t, the cross-sectional dimensions of the continuously cast billet are 165×165mm.

[0111] 1) Nitrogen (N2) is blown into the bottom throughout the converter smelting process. The N2 pressure is 1.28 MPa and the N2 purity is 99.995%.

[0112] 2) The bottom-blown N2 flow rate control at each stage of smelting is shown in the table below:

[0113]

[0114] 3) During converter tapping, [C]: 0.06%, temperature: 1692℃, tapping port (number of furnaces): 38, tapping time: 4 min 4 s. Deoxidizer, slagging agent, carbon powder, deoxidizing alloy, etc., were added according to the operating procedures. The tapped steel sample [N]: 45 ppm. Data from this furnace shows that using the original process, the converter bottom-blown argon gas tapped steel sample [N]: 29 ppm. In this embodiment, the nitrogen content increased by: [N]: 45 - 29 = 16 ppm.

[0115] 4) According to the steel tapping port, use 38 heats. Start adding 100kg of nitrogen-containing alloy bag by bag evenly from 1 minute 15 seconds after tapping, and finish adding it in 1 minute 53 seconds.

[0116] 5) Ladle N2 blowing operation: ① N2 blowing flow rate during tapping stage: 1000m³ 3 / h; ② During the station entry-sampling stage, one sample from the ladle [N]: 142ppm, nitrogen yield: 78%, N2 blowing flow rate: 800m 3 / h; ③ Isostatic stage, N2 flow rate: 150m³ / h; 3 / h; ④ During the supplementary blowing-off stage, two samples from the ladle [N]: 154ppm, blowing N2 flow rate: 200m³ / h. 3 / h.

[0117] 6) Ladle temperature at station: 1543℃, tundish finished product sample [N]: 162ppm.

[0118] The contribution of bottom-blown N2 in the converter [N]: 16 / (162-29)=0.12=12%.

[0119] Example 5:

[0120] Smelting in a 120t converter with a steel output of approximately 125t, the cross-sectional dimensions of the continuously cast billet are: 165×165mm;

[0121] 1) Nitrogen (N2) is blown into the bottom throughout the converter smelting process. N2 pressure: 1.28 MPa, N2 purity: 99.995%.

[0122] 2) The bottom-blown N2 flow rate control at each stage of smelting is shown in the table below:

[0123]

[0124] 3) During converter tapping, [C]: 0.10%, temperature: 1683℃, tapping port (number of furnaces): 45, tapping time: 4 min 1 s. Deoxidizer, slagging agent, carbon powder, deoxidizing alloy, etc., were added according to the operating procedures. The tapped steel sample [N]: 49 ppm. Data from this furnace shows that using the original process, the converter bottom-blown argon gas tapped steel sample [N]: 29 ppm. In this embodiment, the nitrogen content increased by: [N]: 49 - 29 = 20 ppm.

[0125] 4) According to the steel tapping port, use 45 heats. Start adding 100kg of nitrogen-containing alloy bag by bag evenly from 1 minute 15 seconds after tapping, and finish adding it in 1 minute 48 seconds.

[0126] 5) Ladle N2 blowing operation: ① N2 blowing flow rate during tapping stage: 1000m³ 3 / h; ② During the inlet-sampling stage, one sample from the ladle [N]: 122ppm, nitrogen yield: 63%, N2 blowing flow rate: 800m 3 / h; ③ Isostatic stage, N2 flow rate: 250m³ / h; 3 / h; ④ During the supplementary blowing-off stage, two samples from the ladle [N]: 151ppm, blowing N2 flow rate: 250m³ / h; 3 / h.

[0127] 6) Ladle temperature at station: 1539℃, tundish finished product sample [N]: 157ppm.

[0128] The contribution of bottom-blown N2 in the converter [N]: 20 / (157-29)=0.156=15.6%.

[0129] Example 5: When the nitrogen content of the ladle sample was 151 ppm, but the actual N2 flow rate during the make-up blow-off stage was 250 m³ / h... 3 / h, which violates the invention's requirement to use medium-flow make-up blowing, i.e., N2 flow rate during the make-up blowing-off stage: 301~400m³ / h. 3 / h, finished product sample [N]: 157ppm, resulting in the steel reinforcement strength-to-yield ratio index failing to meet the standard.

[0130] The high-nitrogen steels obtained in Examples 1, 2, 3, and 4 are rolled into coiled and straight rebars with diameters ranging from 8mm to 40mm. In this embodiment, the rebar code is seismic-resistant threaded steel HRB500E. Performance indicators are shown in the table below.

[0131]

[0132] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this application. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0133] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0134] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A method for producing high-nitrogen steel, characterized in that, Used for the production of high-nitrogen steel of model HRB500E, including ladles selected to be matched with converters ranging from 80t to 150t; Nitrogen gas is blown into the ladle; N2 flow rate during the tapping stage: 1000~1500 m³ / h 3 / h; N2 flow rate during the inlet-sampling stage: 800~1200 m³ / h 3 / h; N2 flow rate during the isostatic stage: 100~300 m³ / h 3 / h; N2 flow rate during the make-up blow-off phase: 200~600 m³ / h 3 / h.

2. The method for producing high-nitrogen steel according to claim 1, characterized in that, Based on the nitrogen content results of the ladle samples, the following N2 flow rate control was implemented: When the nitrogen content of the ladle sample meets the target nitrogen content, the N2 flow rate during the replenishment-departure stage is 200~300 m³ / h. 3 / h; When the nitrogen content of the ladle sample is less than the target nitrogen content, the N2 flow rate during the replenishment-departure stage is 301~600 m³ / h. 3 / h.

3. The method for producing high-nitrogen steel according to claim 1, characterized in that, The N2 flow rate during the tapping stage is 1000~1300 m³ / h. 3 / h; N2 flow rate during the inlet-sampling stage: 800~1000m³ 3 / h; N2 flow rate during the isostatic stage: 100~200 m³ / h 3 / h.

4. The method for producing high-nitrogen steel according to claim 1, characterized in that, It also includes tapping, which is the pouring of molten steel from the tapping port of the converter into the ladle; After tapping begins, n seconds later, a nitrogen-containing alloy is added to the ladle. The addition time for the nitrogen-containing alloy is m seconds. As the number of furnaces using the tapping outlet increases, n gradually decreases to a set value and then remains constant, and m gradually decreases to a set value and then remains constant.

5. The method for producing high-nitrogen steel according to claim 4, characterized in that, The tapping port is used for 1 to 20 heats, n is 80 to 150, and m is 120 to 150. The tapping port is used for 21 to 50 heats, n is 70 to 79, and m ranges from 90 to 120; The tapping port is used for 51 to 130 heats, n is 60 to 69, and m is 60 to 90. The tapping port is used for more than 130 heats, n is less than 60, and m ranges from 30 to 60.

6. The method for producing high-nitrogen steel according to claim 5, characterized in that, The tapping port is used more than 130 heats, and the range of m is 42~60.

7. The method for producing high-nitrogen steel according to claim 1, characterized in that, It also includes the converter smelting process; In the converter smelting process, N2 is continuously blown into the bottom of the converter.

8. The method for producing high-nitrogen steel according to claim 7, characterized in that, The converter smelting process includes slag splashing, ferroalling, blowing, secondary lance sampling, spot blowing, manual sampling, sample waiting, and tapping stages; among which... The flow rate of N2 introduced during the slag splashing stage is 800 m³ / s. 3 / h; The flow rate of N2 introduced during the iron mixing stage is 360 m³. 3 / h; The flow rate of N2 introduced during the blowing stage is 280~420 m³ / h. 3 / h; The flow rate of N2 introduced during the secondary gun sampling stage is 200~300m³. 3 / h; The flow rate of N2 introduced during the initial blowing stage is 280~420m³. 3 / h; The flow rate of N2 introduced during the manual sampling stage is 200~300m³. 3 / h; The flow rate of N2 introduced during the isostatic stage is 200~300 m³ / h. 3 / h; The flow rate of N2 introduced during the tapping stage is 200~300 m³ / h. 3 / h.

9. The method for producing high-nitrogen steel according to claim 7, characterized in that, The flow control during the blowing, auxiliary lance sampling, spot blowing, manual sampling, equal sampling, and tapping stages of the converter smelting is as follows: The flow rate of N2 introduced during the blowing stage is 300~400 m³ / h. 3 / h; The flow rate of N2 introduced during the secondary gun sampling stage is 250~280m³. 3 / h; The flow rate of N2 introduced during the initial blowing stage is 300~400m³. 3 / h; The flow rate of N2 introduced during the manual sampling stage is 250~280m³. 3 / h; The flow rate of N2 introduced during the isostatic stage is 250~280 m³ / h. 3 / h; The flow rate of N2 introduced during the tapping stage is 250~280 m³ / h. 3 / h.

Images