A method for controlling a staged low gun position converter steelmaking

Abstract

This invention discloses a graded low-lance position control method for converter steelmaking, belonging to the field of top-and-bottom combined blowing converter steelmaking technology. The method divides the entire blowing process into four stages according to the smelting reaction progress: ignition and heating stage, dephosphorization and slagging stage, intense decarburization reaction stage, and final carbon removal stage. The oxygen lance position in each stage is controlled according to a progressively lowering gradient low-lance position range, and the oxygen supply flow rate, bottom blowing gas supply intensity, and slagging material feeding sequence are linked and adjusted. The lance position is the vertical height of the oxygen lance nozzle from the molten pool surface. This invention is applicable to the industrial batch smelting of steel grades such as plain carbon steel, low alloy steel, high carbon steel, and low carbon cold-rolled base materials. It adopts a four-stage progressively lowering gradient low-lance position control, linking and matching the oxygen supply flow rate, bottom blowing gas supply intensity, and slagging material feeding sequence; it enhances molten pool stirring, stabilizes the carbon-oxygen reaction, reduces the iron oxide content in the slag, suppresses splashing, shortens the smelting time, and stabilizes the final steel composition.

Description

Technical Field

[0001] This invention belongs to the field of top and bottom blowing converter steelmaking technology, and in particular relates to a method for controlling the steelmaking process of a staged low-lance converter. Background Technology

[0002] The 180t top-and-bottom blown converter is the mainstream smelting equipment for carbon steel and low alloy steel. Conventional smelting generally adopts a fluctuating lance position system, which involves a high lance position in the early stage, a lower lance position in the middle stage, and a higher lance position in the later stage. In the early stage, the oxygen lance position is too high, resulting in insufficient depth of oxygen jet impact on the molten pool, weak kinetic energy of molten pool stirring, slow lime melting speed, and delayed slag formation. In order to optimize the slag formation effect, the operator frequently raises and lowers the oxygen lance, causing large fluctuations in lance position, resulting in disordered oxygen jet impact position and poor stability of carbon-oxygen reaction.

[0003] The existing process has the following drawbacks: 1. Uneven stirring of the molten pool, local over-oxidation of the molten pool, high TFe content in the final slag, and increased burn-off of steel material; 2. Violent foaming of the foamy slag can easily cause splashing at the furnace mouth, resulting in severe steel loss and accelerated wear of furnace mouth components; 3. The decarbonization reaction rate fluctuates greatly, resulting in a long overall smelting and blowing cycle; 4. The endpoint carbon, temperature, and residual phosphorus content fluctuate greatly, and the single-shot hit rate of the secondary gun is low.

[0004] Most existing low-lance position processes only temporarily lower the lance position during the decarburization stage, without setting gradient segmented low-lance position intervals according to the smelting reaction cycle. They also lack coordinated constraints on oxygen supply flow rate, bottom blowing gas intensity, and slag-forming charging sequence. Long-term ultra-low lance position operation easily leads to erosion of the furnace bottom, blurring process parameter boundaries and making it difficult to stably replicate industrially. Therefore, there is an urgent need for a four-stage gradient low-lance position, multi-parameter linkage control scheme to solve the technical pain points of high splash rate, high final slag total iron content, long smelting cycle, and unstable final composition. Summary of the Invention

[0005] To address the aforementioned technical deficiencies, this invention provides a graded low-lance position converter steelmaking control method, overcoming the shortcomings of existing technologies such as frequent and significant fluctuations in lance position, uneven molten pool agitation, high TFe content in final slag, frequent splashing, and large fluctuations in endpoint indicators. It employs a four-stage, progressively lowering gradient low-lance position control method, linking and matching oxygen supply flow rate, bottom blowing gas supply intensity, and slag-forming and feeding sequence; it enhances molten pool agitation, stabilizes the carbon-oxygen reaction, reduces iron oxide content in slag, suppresses splashing, shortens smelting time, and stabilizes the final steel composition.

[0006] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution: A graded low-lance position control method for steelmaking in a converter is applied to a top-and-bottom combined blowing converter. The entire blowing process is divided into the ignition and heating stage, the dephosphorization and slag-forming stage, the intense decarburization reaction stage, and the final carbon removal stage according to the smelting reaction process. The oxygen lance position in each stage is controlled according to a gradient low-lance position range with progressively lower pressure, and the oxygen supply flow rate, bottom blowing gas supply intensity, and slag-forming material addition sequence are linked and regulated. The lance position is the vertical height of the oxygen lance nozzle from the molten pool surface. The ignition and heating stage is from the start of blowing to 60 seconds, with the oxygen lance position at 1750-1900 mm, the oxygen supply flow rate at 70%-79% of the rated oxygen supply flow rate, and the bottom blowing gas supply intensity at 0.08-0.10 Nm³ / (t·min). No slag-forming material is added during this stage. The dephosphorization and slag-forming stage is from 60s to 280-320s after the start of blowing, the oxygen lance position is 1150-1300mm, the oxygen supply flow rate is 92%-100% of the rated oxygen supply flow rate, the bottom blowing gas supply intensity is 0.12-0.15Nm³ / (t·min), and the slag-forming material is added in at least two batches. The intense decarbonization reaction stage lasts from the end of the dephosphorization and slag-forming stage to 700–730 seconds after the start of blowing. The oxygen lance position is 950–1100 mm, the oxygen supply flow rate is maintained at the rated oxygen supply flow rate, and the bottom blowing gas supply intensity is 0.14–0.16 Nm³ / (t·min). The final carbon extraction stage lasts from the end of the intense decarburization reaction stage until tapping; before the auxiliary lance temperature measurement and sampling, the oxygen lance position is maintained at 880-980 mm; after the auxiliary lance test is completed, the oxygen lance position is lowered to 780-860 mm, the oxygen supply flow rate is reduced to 80%-90% of the rated oxygen supply flow rate, the bottom blowing gas supply intensity is 0.09-0.11 Nm³ / (t·min), and the low-pressure lance is stabilized for blowing for 15-30 s.

[0007] Preferably, the nominal capacity of the converter is 180t.

[0008] Preferably, the oxygen lance has a rated oxygen supply flow rate of 34,000 Nm³ / h, and the oxygen lance nozzle is a four-hole nozzle.

[0009] Preferably, during the dephosphorization and slag-forming stage, 75% of the total slag-forming material is added during the 60s blowing process, and the remaining 25% of the slag-forming material is added during the 180s blowing process.

[0010] Preferably, the total amount of slag-forming material per ton of steel is 11-13 kg / t, and the slag-forming material includes lime and lightly calcined dolomite, with lime accounting for 68%-74% of the mass of the slag-forming material; in addition, 0.5-1 kg / t of slag-forming agent is added per ton of steel.

[0011] Preferably, the oxygen lance is only fine-tuned within the corresponding stage's lance position range throughout the smelting process, and lance position fluctuations exceeding ±150mm are prohibited.

[0012] Preferably, during the intense decarburization reaction stage, the flue gas state at the furnace mouth and the slag foaming state are monitored in real time. When the slag becomes dry again, 0.3 to 0.6 kg / t of slag-forming agent is added at one time.

[0013] Preferably, nitrogen is used as the bottom blowing gas in the early stage of blowing, and argon is switched to stir after the carbon content of the molten pool drops to 0.6%.

[0014] Preferably, during the final carbon extraction stage, the stoking time of the pressurized lance is 25-30 seconds when smelting low-carbon steel, and 15-20 seconds when smelting medium- and high-carbon steel.

[0015] Preferably, the steel grades smelted include plain carbon steel, low alloy steel, high carbon steel, and low carbon cold-rolled base material.

[0016] The advantages and technical effects of this invention are: This invention employs a gradient gun position to stabilize the jet impact position and ensure uniform stirring of the molten pool: the entire process adopts a segmented low gun position system with progressively decreasing pressure, eliminating the large fluctuations in gun position caused by the high-low-high in traditional processes. This stabilizes the position of the oxygen jet impacting the molten pool and significantly improves the overall uniformity of stirring of the molten pool. This effect corresponds to the technical feature of this invention, which sets gradient low gun position intervals at each stage and prohibits large fluctuations in gun position.

[0017] This invention can accelerate slag formation and inhibit FeO enrichment: the low gun position in the early stage accelerates lime melting, generates high-basicity slag in advance, and the dephosphorization effect is stable; the carbon-oxygen reaction is stable and controllable, inhibiting FeO enrichment, and the TFe mass fraction of the final slag is reduced by about 24% compared with the traditional process, and the burning loss of steel materials is reduced; this effect corresponds to the technical characteristics of the linkage between gun position, oxygen supply flow rate and bottom blowing intensity in the dephosphorization slag formation stage and the intense decarburization reaction stage.

[0018] This invention can suppress splashing: the reaction state of the molten pool is stable, the height of the foam slag is controllable, and the incidence of metal splashing accidents is reduced by more than 45% compared with traditional processes; this effect corresponds to the technical features of step-by-step lowering of the gun position, batch feeding of slag-forming materials, and prohibition of large fluctuations in the gun position throughout the process.

[0019] This invention can shorten the smelting cycle: the coordinated control of multiple parameters such as gun position, oxygen supply, and bottom blowing stabilizes and accelerates the decarburization reaction rate, and the overall smelting cycle is shortened by 35 to 85 seconds compared with the traditional process; this effect corresponds to the technical feature of linkage control of gun position, oxygen supply flow rate, and bottom blowing gas supply intensity at each stage.

[0020] This invention can balance furnace lining life: the gradient downward pressure low lance position mode avoids the scouring of the furnace bottom during long-term ultra-low lance position operation, and balances the stirring effect of the molten pool and the service life of the furnace lining; this effect corresponds to the technical features of segmented and step-by-step downward pressure of the lance position at each stage and clear interval boundaries.

[0021] The process parameters in this invention have clear boundaries, and the operation scheme can be directly replicated in industrial production, making it suitable for mass industrial production of steel grades such as plain carbon steel, low alloy steel, high carbon steel, and low carbon cold-rolled base materials. Detailed Implementation

[0022] To make the above-mentioned objectives, control system design, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] In the description of this invention, the lance position refers to the vertical height of the oxygen lance nozzle from the surface of the molten pool; TFe refers to the total iron content (mass fraction) in the slag; the rated oxygen supply flow rate refers to the oxygen supply flow rate corresponding to the oxygen lance blowing at full load as designed; and the slag-forming agent refers to the auxiliary material used to promote lime melting and adjust the slag fluidity.

[0024] A method for controlling steelmaking in a graded low-lance converter is disclosed, applied to a top-and-bottom combined blowing converter with a nominal capacity of 150-200t, preferably 180t. The following detailed description uses a 180t top-and-bottom combined blowing converter from a steel plant as an example. Basic equipment conditions: The rated oxygen supply flow rate of the oxygen lance is 34000 Nm³ / h, and the oxygen lance nozzle is a four-hole nozzle; bottom blowing uses nitrogen and argon gas, switched on a time-separated basis. Nitrogen is used in the early stages of blowing, and argon is switched to for stirring after the carbon content in the molten pool drops to 0.6%.

[0025] The entire blowing process is divided into the following stages according to the smelting reaction progress: ignition and heating stage, dephosphorization and slag formation stage, vigorous decarburization reaction stage, and final carbon removal stage. The control principles of each stage are as follows: Ignition and heating stage (from start to 60s): This stage aims to stabilize the molten pool and increase its temperature. The oxygen lance position is controlled at 1750–1900 mm, the oxygen supply flow rate is 70%–79% of the rated oxygen supply flow rate, and the bottom blowing gas supply intensity is 0.08–0.10 Nm³ / (t·min). No slag-forming material is added during this stage. A moderately low lance position combined with a relatively low oxygen supply flow rate ensures stable ignition of the molten pool, avoids excessively high oxygen supply flow rate in the early stage causing strong oxidation and splashing, and also avoids premature material addition leading to slag-forming material agglomeration.

[0026] Dephosphorization and slag-forming stage (60s to 280-320s after blowing): This stage aims for rapid slag formation and efficient dephosphorization. The oxygen lance position is lowered to 1150-1300mm, the oxygen supply flow rate is increased to 92%-100% of the rated oxygen supply flow rate, and the bottom blowing gas supply intensity is increased to 0.12-0.15 Nm³ / (t·min). The low-position oxygen jet impact strengthens the stirring of the molten pool, accelerates lime melting, and rapidly generates high-alkalinity oxide slag in the early stage, completing efficient dephosphorization; the slag-forming material is added in at least two batches to avoid cooling and splashing of the molten pool caused by a large amount of material added at once.

[0027] Intense decarburization reaction stage (from the end of the dephosphorization and slag-forming stage to 700–730 s after the start of blowing): This stage aims for stable and efficient decarburization. The oxygen lance position is further lowered to 950–1100 mm, the oxygen supply flow rate is maintained at the rated full load flow rate, and the bottom blowing gas supply intensity is 0.14–0.16 Nm³ / (t·min). The constant low lance position deepens the impact pit of the molten pool, strengthens the overall stirring of the molten pool, makes the intense carbon-oxygen reaction stable and controllable, and inhibits the enrichment of a large amount of FeO into the slag.

[0028] Final carbon extraction stage (from the end of the intense decarburization reaction stage to tapping): This stage aims to precisely control the final carbon content and temperature. Before the auxiliary lance temperature measurement and sampling, the oxygen lance position is maintained at 880-980 mm; after receiving the auxiliary lance carbon temperature detection data, the oxygen lance position is lowered to 780-860 mm, the oxygen supply flow rate is reduced to 80%-90% of the rated oxygen supply flow rate, the bottom blowing gas supply intensity is reduced to 0.09-0.11 Nm³ / (t·min), and low-pressure lance stabilization blowing is carried out for 15-30 seconds to accurately lock the final carbon content and avoid over-oxidation of molten steel.

[0029] Throughout the smelting process, the oxygen lance is only finely adjusted within the corresponding lance position range. Large fluctuations exceeding ±150mm are prohibited to avoid frequent lance raising and lowering causing the oxygen jet to impact the position in disorder. At the same time, since the lance position is lowered in stages and steps rather than operating at a single ultra-low lance position for a long time, the oxygen jet is prevented from eroding the furnace bottom, thus balancing the stirring effect of the molten pool and the service life of the furnace lining.

[0030] Example 1: Smelting of Q235B ordinary carbon steel 1) Raw material conditions for furnace feeding: Iron composition (mass fraction): C=4.21%, Si=0.46%, Mn=0.61%, P=0.079%, S=0.028%; Iron temperature 1322℃; Scrap steel ratio 15%.

[0031] 2) Slag-forming system: The total amount of slag material per ton of steel is 12.0 kg / t, including 8.2 kg / t of lime, 3.0 kg / t of lightly calcined dolomite, and 0.8 kg / t of slag-forming agent; the slag material is added in two batches.

[0032] 3) Segmented process parameters: ① Ignition and heating stage 0~60s: gun position 1820mm; oxygen supply flow rate 26000 Nm³ / h; bottom blowing gas supply intensity 0.09Nm³ / (t·min); no slag-forming material is added.

[0033] ② Dephosphorization and slag-forming stage 60~300s: gun position 1220mm; oxygen supply flow rate 33000 Nm³ / h; bottom blowing gas supply intensity 0.13 Nm³ / (t·min); 75% of the total slag-forming material is added after 60s of blowing, and the remaining 25% of the slag-forming material is added after 180s of blowing.

[0034] ③ Intense decarbonization reaction stage 300~720s: gun position 1020mm; oxygen supply flow rate 34000 Nm³ / h; bottom blowing gas supply intensity 0.15 Nm³ / (t·min).

[0035] ④ Final carbon extraction stage: 720-840s, gun position 920mm; after the auxiliary gun inspection, lower the gun position to 830mm; oxygen supply flow rate 29500 Nm³ / h; bottom blowing gas supply intensity 0.10 Nm³ / (t·min); press the gun and stabilize the blowing pressure for 20s.

[0036] 4) Smelting results: Total blowing time 895s; final carbon content 0.062%, final temperature 1678℃, final phosphorus content 0.012%; final slag TFe=12.3%; oxygen consumption per ton of steel 47.8 Nm³; no obvious splashing throughout the smelting process.

[0037] Example 2: Smelting of Q355B low alloy steel 1) Raw material conditions for furnace feeding: Iron composition (mass fraction): C=4.30%, Si=0.51%, Mn=0.68%, P=0.088%, S=0.024%; Iron temperature 1331℃; Scrap steel ratio 18%.

[0038] 2) Slag-forming system: The total amount of slag material per ton of steel is 13.0 kg / t, including 8.6 kg / t of lime, 3.4 kg / t of lightly calcined dolomite, and 1.0 kg / t of slag-forming agent; the slag material is added in two batches.

[0039] 3) Segmented process parameters: ① Ignition and heating stage 0~60s: gun position 1780mm; oxygen supply flow rate 25200 Nm³ / h; bottom blowing gas supply intensity 0.085Nm³ / (t·min); no slag-forming material is added.

[0040] ② Dephosphorization and slag-forming stage 60~320s: gun position 1180mm; oxygen supply flow rate 33400 Nm³ / h; bottom blowing gas supply intensity 0.14 Nm³ / (t·min); slag-forming material is fed in two batches.

[0041] ③ Intense decarbonization reaction stage 320~730s: gun position 980mm; oxygen supply flow rate 34000 Nm³ / h; bottom blowing gas supply intensity 0.16 Nm³ / (t·min).

[0042] ④ Final carbon extraction stage: 730~865s, gun position 900mm; after the auxiliary gun sampling is completed, press the gun position down to 810mm; oxygen supply flow rate 28800 Nm³ / h; bottom blowing gas supply intensity 0.095 Nm³ / (t·min); press the gun and stabilize the blowing pressure for 25s.

[0043] 4) Smelting results: Total blowing time 925s; final carbon content 0.121%, final temperature 1689℃, final phosphorus content 0.013%; final slag TFe=12.8%; oxygen consumption per ton of steel 48.7 Nm³; stable slag formation with no obvious splashing.

[0044] Example 3: Smelting of 45# High Carbon Steel 1) Raw material conditions for furnace feeding: Iron composition (mass fraction): C=4.38%, Si=0.36%, Mn=0.79%, P=0.068%, S=0.029%; Iron temperature 1313℃; Scrap steel ratio 12%.

[0045] 2) Slag-forming system: The total amount of slag material per ton of steel is 11.0 kg / t, including 7.6 kg / t of lime, 2.9 kg / t of lightly calcined dolomite, and 0.5 kg / t of slag-forming agent; the slag material is added in two batches.

[0046] 3) Segmented process parameters: ① Ignition and heating stage 0~60s: gun position 1880mm; oxygen supply flow rate 26800 Nm³ / h; bottom blowing gas supply intensity 0.10Nm³ / (t·min); no slag-forming material is added.

[0047] ② Dephosphorization and slag-forming stage 60~280s: gun position 1260mm; oxygen supply flow rate 32600 Nm³ / h; bottom blowing gas supply intensity 0.125 Nm³ / (t·min); slag-forming material is fed in two batches.

[0048] ③ Intense decarbonization reaction stage 280~710s: gun position 1060mm; oxygen supply flow rate 34000 Nm³ / h; bottom blowing gas supply intensity 0.14 Nm³ / (t·min).

[0049] ④ Final carbon pulling stage: 710~825s gun position 940mm; after the auxiliary gun inspection, press the gun position down to 850mm; oxygen supply flow rate 30500 Nm³ / h; bottom blowing gas supply intensity 0.10 Nm³ / (t·min); press the gun and stabilize the blowing pressure for 15s.

[0050] 4) Smelting results: Total blowing time 875s; final carbon content 0.423%, final temperature 1671℃, final phosphorus content 0.011%; final slag TFe=11.6%; oxygen consumption per ton of steel 46.9 Nm³; final carbon content was controlled stably with no obvious splashing.

[0051] Example 4: Smelting of SPHC low-carbon cold-rolled base material 1) Raw material conditions for furnace feeding: Iron composition (mass fraction): C=4.12%, Si=0.41%, Mn=0.52%, P=0.084%, S=0.021%; Iron temperature 1324℃; Scrap steel ratio 20%.

[0052] 2) Slag-forming system: The total amount of slag material per ton of steel is 12.5 kg / t, including 8.1 kg / t of lime, 3.4 kg / t of lightly calcined dolomite, and 1.0 kg / t of slag-forming agent; the slag material is added in two batches.

[0053] 3) Segmented process parameters: ① Ignition and heating stage 0~60s: gun position 1760mm; oxygen supply flow rate 24100 Nm³ / h; bottom blowing gas supply intensity 0.08Nm³ / (t·min); no slag-forming material is added.

[0054] ② Dephosphorization and slag-forming stage 60~300s: gun position 1160mm; oxygen supply flow rate 32900 Nm³ / h; bottom blowing gas supply intensity 0.15 Nm³ / (t·min); slag-forming material is fed in two batches.

[0055] ③ Intense decarbonization reaction stage 300~700s: gun position 960mm; oxygen supply flow rate 34000 Nm³ / h; bottom blowing gas supply intensity 0.16 Nm³ / (t·min).

[0056] ④ Final carbon extraction stage: 700-850s, gun position 890mm; after the auxiliary gun sampling is completed, press the gun position down to 790mm; oxygen supply flow rate 27600 Nm³ / h; bottom blowing gas supply intensity 0.09 Nm³ / (t·min); press the gun and stabilize the blowing pressure for 30s.

[0057] 4) Smelting results: Total blowing time 905s; final carbon content 0.029%, final temperature 1684℃, final phosphorus content 0.014%; final slag TFe=13.1%; oxygen consumption per ton of steel 49.6 Nm³; low carbon steel showed no over-oxidation and no obvious splashing.

[0058] Comparative Example: Traditional Process Control Test Using the same furnace conditions and raw material conditions as the above embodiments, a comparative smelting process was conducted according to the traditional high-low-high fluctuation lance position process, i.e., high lance position in the early stage, lowered lance in the middle stage, and raised lance in the later stage, with frequent and large fluctuations in lance position during the blowing process. Comparative results: The control group had an average final slag TFe of 16.2%, an average blowing time of 960s, and a significantly higher smelting splashing rate than the method of this invention.

[0059] Under the same conditions, the final slag TFe content of the method of the present invention is 11.6% to 13.1%, which is about 24% lower than that of the control group; the blowing time is 875 to 925 s, which is 35 to 85 s shorter than that of the control group; there is no obvious splashing throughout the process, and all smelting indicators are significantly better than those of the control group.

[0060] Table 1 Summary of Smelting Indicators for Examples

[0061] Table 2 Raw material condition parameters

[0062] Table 3. Process parameters for staged gun positions, oxygen supply, and bottom blowing.

[0063] As can be seen from the above embodiments and comparative data, in the smelting of four types of steel—Q235B plain carbon steel, Q355B low alloy steel, 45# high carbon steel, and SPHC low carbon cold-rolled base material—the present invention achieves a final slag TFe content of 11.6%–13.1%, a residual phosphorus content of 0.011%–0.014%, and a total blowing time of 875–925 s with no significant splashing throughout the process. All indicators are significantly better than the control group using the traditional fluctuating gun position process, making it suitable for large-scale industrial smelting.

[0064] The above supplementary embodiments fully demonstrate that the method of the present invention exhibits stable low-temperature melting effect and excellent metallurgical quality improvement capability under different steel grades and different process parameter boundary conditions, and its comprehensive performance is far superior to traditional fluorite process and single-component modification scheme.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling steelmaking in a staged low-lance converter, applied to a top-and-bottom combined blowing converter, characterized in that, The entire blowing process is divided into the ignition and heating stage, the dephosphorization and slag-forming stage, the decarburization and intense reaction stage, and the final carbon removal stage according to the smelting reaction process. The oxygen lance position in each stage is controlled according to the gradient low lance position range of step-by-step pressure, and the oxygen supply flow rate, bottom blowing gas supply intensity, and slag-forming material feeding sequence are linked and controlled. The lance position is the vertical height of the oxygen lance nozzle from the molten pool surface. The ignition and heating stage is from the start of blowing to 60 seconds, with the oxygen lance position at 1750-1900 mm, the oxygen supply flow rate at 70%-79% of the rated oxygen supply flow rate, and the bottom blowing gas supply intensity at 0.08-0.10 Nm³ / (t·min). No slag-forming material is added during this stage. The dephosphorization and slag-forming stage is from 60s to 280-320s after the start of blowing, the oxygen lance position is 1150-1300mm, the oxygen supply flow rate is 92%-100% of the rated oxygen supply flow rate, the bottom blowing gas supply intensity is 0.12-0.15Nm³ / (t·min), and the slag-forming material is added in at least two batches. The intense decarbonization reaction stage lasts from the end of the dephosphorization and slag-forming stage to 700–730 seconds after the start of blowing. The oxygen lance position is 950–1100 mm, the oxygen supply flow rate is maintained at the rated oxygen supply flow rate, and the bottom blowing gas supply intensity is 0.14–0.16 Nm³ / (t·min). The final carbon extraction stage lasts from the end of the intense decarburization reaction stage until tapping; before the auxiliary lance temperature measurement and sampling, the oxygen lance position is maintained at 880-980 mm; after the auxiliary lance test is completed, the oxygen lance position is lowered to 780-860 mm, the oxygen supply flow rate is reduced to 80%-90% of the rated oxygen supply flow rate, the bottom blowing gas supply intensity is 0.09-0.11 Nm³ / (t·min), and the low-pressure lance is stabilized for blowing for 15-30 s.

2. The method for controlling the staged low-lance position converter steelmaking according to claim 1, characterized in that, The nominal capacity of the converter is 180t.

3. The method for controlling the staged low-lance position converter steelmaking according to claim 2, characterized in that, The oxygen lance has a rated oxygen supply flow rate of 34,000 Nm³ / h, and the oxygen lance nozzle is a four-hole nozzle.

4. The method for controlling the staged low-lance position converter steelmaking according to claim 2, characterized in that, During the dephosphorization and slag-forming stage, 75% of the total slag-forming material is added after 60 seconds of blowing, and the remaining 25% of the slag-forming material is added after 180 seconds of blowing.

5. The method for controlling the staged low-lance position converter steelmaking according to claim 2, characterized in that, The total amount of slag-forming material used per ton of steel is 11-13 kg / t. The slag-forming material includes lime and lightly calcined dolomite, with lime accounting for 68%-74% of the mass of the slag-forming material. In addition, 0.5-1 kg / t of slag-forming agent is added per ton of steel.

6. The method for controlling the staged low-lance position converter steelmaking according to claim 2, characterized in that, Throughout the smelting process, the oxygen lance is only fine-tuned within the corresponding stage's lance position range, and lance position fluctuations exceeding ±150mm are prohibited.

7. The method for controlling the staged low-lance position converter steelmaking according to claim 2, characterized in that, During the intense decarbonization reaction stage, the flue gas status at the furnace mouth and the foaming status of the slag are monitored in real time. When the slag becomes dry again, 0.3 to 0.6 kg / t of slag-forming agent is added at one time.

8. The method for controlling the staged low-lance position converter steelmaking according to claim 2, characterized in that: Nitrogen is used as the bottom blowing gas in the early stage of the blowing process. After the carbon content of the molten pool drops to 0.6%, argon is switched to the gas for stirring.

9. The method for controlling the staged low-lance position converter steelmaking according to claim 2, characterized in that, During the final carbon extraction stage, the stoking time of the pressurized lance should be 25-30 seconds when smelting low-carbon steel, and 15-20 seconds when smelting medium- and high-carbon steel.

10. The method for controlling graded low-lance position converter steelmaking according to any one of claims 1-9, characterized in that: The steel grades smelted include plain carbon steel, low alloy steel, high carbon steel, and low carbon cold-rolled base material.

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