A low-melt ratio smelting method suitable for an automatic steelmaking model

Abstract

The application belongs to the technical field of steel smelting, and particularly discloses a low-molten-iron-ratio smelting method suitable for an automatic steel smelting model, which comprises four stages, namely, a blowing starting ignition stage, an early molten pool temperature rising stage, a middle slagging smelting stage and a terminal temperature and carbon control stage.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and specifically to a low-iron-ratio smelting method suitable for automated steelmaking models. Background Technology

[0002] Low-iron-to-metal ratio smelting is an important technological direction for the steel industry to achieve green and low-carbon production. However, in practical application, it has been found that due to the significant increase in the proportion of scrap steel charged into the furnace, it absorbs a large amount of heat in the early stages of smelting, resulting in a persistently low temperature in the molten pool. This fundamental problem triggers a series of chain reactions: the molten pool temperature rise is severely delayed in the early stages of smelting, making it difficult to quickly reach the temperature required for the carbon-oxygen reaction. This not only directly causes difficulties in lime melting and slow initial slag formation leading to low dephosphorization efficiency, but also frequently causes splashing due to uneven reactions within the molten pool and unstable gas release.

[0003] Existing automated steelmaking models are mostly developed based on conventional hot metal ratio conditions. Their oxygen supply and slag formation control modes cannot adapt to the rapid changes in early-stage thermal state and slag characteristics under "low hot metal ratio" conditions. Therefore, under low iron consumption modes, problems such as process runaway, frequent splashing, and low endpoint hit rate are common. Although the industry has tried to adjust the batching and staged oxygenation, these measures often lack a systematic approach and fail to fundamentally solve the dynamic matching problem between early-stage heat shortage and slag formation requirements, making it difficult to achieve stable and automated smelting control.

[0004] Therefore, it is necessary to develop an automated smelting mode that can be specifically adapted to the early-stage characteristics of smelting under "low iron-to-water ratio" conditions and achieve rapid heating and slag formation synergistic control, so as to ensure smooth process operation and accurate end-point control. Summary of the Invention

[0005] The purpose of this invention is to provide a low-iron-ratio smelting method suitable for automated steelmaking models, in order to solve the problem of delayed heating of the molten pool in the early stage of smelting under low-iron-ratio conditions, which leads to unstable subsequent operating conditions.

[0006] To achieve the above objectives, the basic solution provided by this invention is: a low-iron-ratio smelting method suitable for automated steelmaking models, characterized by comprising four stages: initial blowing and ignition, early-stage molten pool heating, mid-stage slag formation and smelting, and final-stage temperature and carbon control. The specific details are as follows: Ignition and blowing stage: During the oxygen step of 0%-3%, ignition is carried out using the ignition gun position and the first oxygen supply intensity. After ignition, when the oxygen step reaches 3%, the oxygen gun is lowered to the blowing gun position and the first oxygen supply intensity is maintained. At the same time, the first bottom blowing flow rate is used, and the first batch of slag is added. In the early stage of molten pool heating: Before the oxygen step reaches 15%, maintain a low lance position and high oxygen supply intensity. When the oxygen step reaches 15%, raise the oxygen lance to the slag-forming lance position and adopt the second oxygen supply intensity, while adding all the coke. Mid-term slag smelting stage: During the oxygen step of 15%-40%, the second oxygen supply intensity is continuously used, and the oxygen lance is gradually reduced to the open blowing position. When the oxygen step reaches 40%, the third oxygen supply intensity is switched and the second bottom blowing flow rate is used. Final temperature and carbon control stage: When the oxygen step reaches 80%, the slag-forming operation is carried out by changing the lance position. After the slag-forming is completed, the oxygen lance is lowered to the carbon-pulling lance position and the fourth oxygen supply intensity is adopted. At the same time, the first bottom blowing flow rate is switched to perform the final carbon-pulling operation.

[0007] The working principle of this invention is as follows: taking the oxygen blowing step as the core of timing control, a four-stage standardized closed-loop control logic adapted to the automatic steelmaking model is constructed. During the oxygen step from 0% to 3%, stable ignition is achieved using the ignition gun position and the first oxygen supply intensity. Upon reaching 3%, the oxygen supply intensity is reduced to the blowing gun position, maintaining the first oxygen supply intensity, simultaneously activating the first bottom blowing flow rate and adding the first batch of slag. Before 15% of the oxygen step, a low gun position and high oxygen supply intensity are maintained. At 15%, the slag-forming gun position and the second oxygen supply intensity are switched, and the full amount of coke is added. From 15% to 40% of the oxygen step, the second oxygen supply intensity is maintained, and the gun position gradually decreases. At 40%, the third oxygen supply intensity and the second bottom blowing flow rate are switched. After slag formation with a different gun position is completed at 80% of the oxygen step, the carbon-pulling gun position, the fourth oxygen supply intensity, and the first bottom blowing flow rate are switched to complete the final carbon-pulling operation. The entire process is adapted to the standardized smelting logic of automatic steelmaking, which links the top and bottom blowing parameters with the addition of auxiliary materials, and is compatible with the programmed execution of the automatic steelmaking model.

[0008] The beneficial effects of this invention are as follows: This method achieves stable ignition, rapid heating and scrap steel melting, smooth slag formation and dephosphorization, and precise temperature and carbon control at the endpoint by precisely matching the oxygen lance position, oxygen supply intensity, bottom blowing flow rate, and auxiliary material addition timing in stages. The entire process forms a standardized closed-loop control, solving the core problem of instability in the smelting process under low iron ratio conditions. It realizes the normalized and stable operation of automatic steelmaking in converters under iron ratio ≤70%, and solves the industry pain points commonly found in low iron ratio smelting, such as low ignition success rate, low-temperature slag overflow in the early stage, slag return and sticking to the lance, and low endpoint component temperature hit rate. The standardized oxygen step timing control throughout the process improves the stability of the smelting process, scrap steel melting efficiency, and endpoint double hit rate, effectively making up for the heat input gap under low iron ratio conditions, and ensuring the dephosphorization effect and steel quality.

[0009] Option 2 is an optimal choice of the basic option. The specific heights of the different lance positions are as follows: the ignition lance position is 2200mm above the liquid surface; the blowing lance position is 1400mm above the liquid surface; the slag-forming lance position is 1800mm above the liquid surface; the carbon-pulling lance position is 1000mm above the liquid surface; the slag-forming operation with different lance positions is as follows: first lower the oxygen lance to a position 1200mm above the liquid surface, and then raise it to a position 1300mm above the liquid surface.

[0010] Option 3, which is the preferred option of Option 2, has a first oxygen supply intensity of 3.7m.3 / t·h, the second oxygen supply intensity is 3.2m 3 / t·h, the third oxygen supply intensity is 3.45m 3 / t·h, the fourth oxygen supply intensity is 3.2m 3 / t·h; the first bottom blowing flow rate is 360m³ / t·h. 3 / h, the second bottom blowing flow rate is 240m³ / h. 3 / h.

[0011] Option 4, which is the preferred option of Option 3, involves adding the first batch of slag in batches during the initial blowing and ignition stage. When the oxygen level reaches 3%, 40% of the total amount of lime and 50% of the total amount of magnesium balls are added. When the oxygen level reaches 8%, 30% of the total amount of lime is added.

[0012] Option 5, a preferred option of Option 4, involves performing a slag disturbance operation every 5% of the oxygen step rate during the mid-term slag smelting stage, when the oxygen step rate is between 15% and 40%. Specifically, the top-blown oxygen lance position is temporarily raised by 200mm, maintained for 1% of the oxygen step rate, and then returned to its original position. Simultaneously, the bottom-blown flow rate is temporarily increased to 300m³ / h. 3 / h, starts and stops synchronously with the gun position adjustment.

[0013] Option 6, which is the preferred option of Option 5, involves controlling the operation time of lowering the lance and pulling carbon in the final temperature and carbon control stage to ≥60s, and continuously stirring the molten pool until the blowing process is terminated.

[0014] Option 7, an optimized version of Option 6, involves real-time monitoring of the furnace mouth flue gas composition and the ferrous oxide mass fraction in the molten pool slag during the final temperature and carbon control stage, while the oxygen concentration is between 80% and 100%. When the detected ferrous oxide mass fraction is <15%, the top-blown oxygen lance position is raised by 100mm. The original position is restored once the ferrous oxide mass fraction recovers to the 15%-20% range. When the ferrous oxide mass fraction is >20%, the top-blown oxygen supply intensity is increased by 0.1m. 3 / (t·h), when the ferrous oxide mass fraction drops back to the 15%-20% range, restore the original oxygen supply intensity. Attached Figure Description

[0015] Figure 1 This is a flowchart of a low-iron-ratio smelting method applicable to an automated steelmaking model according to the present invention. Detailed Implementation

[0016] The present invention will be further described in detail below through specific embodiments: Example like Figure 1 The following describes a low-iron-ratio smelting method suitable for automated steelmaking models, comprising four stages: initial blowing and ignition, early-stage molten pool heating, mid-stage slag formation and smelting, and final-stage temperature and carbon control. The specific details are as follows: Ignition and initial blowing stage: During the oxygen step of 0%-3%, ignition is carried out using the ignition gun position and the first oxygen supply intensity. After ignition, when the oxygen step reaches 3%, the oxygen gun is lowered to the initial blowing position and the first oxygen supply intensity is maintained. At the same time, the first bottom blowing flow rate is used to add the first batch of slag material in batches. When the oxygen step reaches 3%, 40% of the total amount of lime and 50% of the total amount of magnesium balls are added. When the oxygen step reaches 8%, 30% of the total amount of lime is added. In the early stage of molten pool heating: Before the oxygen step reaches 15%, maintain a low lance position and high oxygen supply intensity. When the oxygen step reaches 15%, raise the oxygen lance to the slag-forming lance position and adopt the second oxygen supply intensity, while adding all the coke. Mid-term slag-forming smelting stage: During the oxygen step of 15%-40%, the second oxygen supply intensity is continuously used, and the oxygen lance is gradually lowered to the open-blowing position. When the oxygen step is within the 15%-40% range, a slag-forming disturbance operation is performed every 5% oxygen step, temporarily raising the position of the top-blown oxygen lance by 200mm, maintaining it for 1% oxygen step duration, and then returning it to the original lance position. At the same time, the bottom-blowing flow rate is temporarily increased to 300m³. 3 / h, starts and stops synchronously with the gun position adjustment. When the oxygen step reaches 40%, it switches to the third oxygen supply intensity and adopts the second bottom blowing flow rate. Final temperature and carbon control stage: When the oxygen step reaches 80%, a slag-forming operation is performed by changing the lance position. After slag formation, the oxygen lance is lowered to the carbon-pulling lance position, and the duration of the lance lowering and carbon-pulling operation is controlled to ≥60s. Molten pool stirring continues until blowing is terminated, and the fourth oxygen supply intensity is adopted. Simultaneously, the first bottom blowing flow rate is switched to perform final carbon-pulling. While the oxygen step is in the 80%-100% range, the composition of the flue gas at the furnace mouth is collected in real time to detect the ferrous oxide mass fraction in the molten pool slag. When the detected ferrous oxide mass fraction is <15%, the top-blown oxygen lance position is raised by 100mm. The original lance position is restored when the ferrous oxide mass fraction returns to the 15%-20% range. When the ferrous oxide mass fraction is higher than 20%, the top-blown oxygen supply intensity is increased by 0.1m. 3 / (t·h), when the ferrous oxide mass fraction falls back to the target range, the original oxygen supply intensity is restored. Wherein: The ignition gun is positioned 2200mm above the liquid surface; The blow gun should be positioned 1400mm above the liquid surface. The slag-removing gun is positioned 1800mm above the liquid surface; The carbon extraction gun is positioned 1000mm above the liquid surface; The initial oxygen supply intensity is 3.7m. 3 / t·h; The second oxygen supply intensity is 3.2m. 3 / t·h; The third oxygen supply intensity is 3.45m. 3 / t·h; The fourth oxygen supply intensity is 3.2m. 3 / t·h; The first bottom blowing flow rate is 360m³. 3 / h; The second bottom blowing flow rate is 240m³. 3 / h; The slag removal operation with variable lance position is as follows: first lower the oxygen lance to a position 1200mm above the liquid surface, and then raise it to a position 1300mm above the liquid surface.

[0017] The implementation method of this embodiment is as follows: Equipment parameters: Nominal capacity 120t top and bottom blowing converter. The top blowing adopts a five-hole Laval oxygen lance with a lance diameter of 273mm. The bottom blowing is equipped with an air supply system of 8 evenly distributed permeable bricks in the ring. It is equipped with an online flue gas analysis system, an automatic feeding system and a furnace mouth pressure control system. The entire process is controlled and dynamically corrected by an automatic steelmaking model. Conditions for charging molten iron: molten iron temperature 1235℃; molten iron composition: C: 4.25%, Si: 0.35%, Mn: 0.28%, P: 0.085%, S: 0.032%; molten iron charge: 78t.

[0018] Scrap steel charging conditions: The graded charging mode is adopted, with a total charging amount of 36t and an overall iron-to-metal ratio of 68.4%, which meets the requirements of low iron-to-metal ratio smelting; 18t of light and thin scrap steel is added as a bottom layer first, followed by 18t of heavy scrap steel.

[0019] Total proportions of smelting auxiliary materials: 4500 kg of lime, 800 kg of magnesium spheres, and 600 kg of coke.

[0020] (1) Perform the ignition and blowing stage operation: During the ignition window of 0%-3% oxygenation, the model-controlled top-blown oxygen lance was precisely positioned 2200mm above the molten pool surface, with the top-blown oxygen supply intensity set at 3.7m. 3 / (t·h), top blowing ignition is performed on the graded scrap steel and molten iron laid in the furnace; during this stage, bottom blowing adopts a pulse gas supply mode with a pulse cycle of 10s and a peak gas supply flow rate of 360m³ / h. 3 / h, peak flow rate 120m 3 / h, duty cycle 1:1, enhances molten pool disturbance during ignition, and avoids ignition failure under low iron ratio conditions.

[0021] Once the oxygen blowing step accurately reaches 3% and the model determines successful ignition based on flue gas data, immediately lower the top-blown oxygen lance to the starting position, 1400mm above the molten pool surface, and maintain it at 3.7m. 3 The first oxygen supply intensity is / (t·h), while the bottom blowing gas flow rate is stably adjusted to 360m³. 3The first bottom blowing flow rate is maintained at a constant rate to ensure maximum molten pool stirring intensity during the initial blowing phase. Simultaneously, the automatic feeding system is triggered to add 1800 kg of lime and 400 kg of magnesium balls into the converter. When the oxygen content reaches 8%, the automatic feeding system adds an additional 1350 kg of lime, completing the addition of the first batch of slag.

[0022] (2) Perform the initial molten pool heating stage operations: During this phase, the automated steelmaking model continuously controls the top-blown oxygen lance to maintain a low blowing position of 1400mm, and the oxygen supply intensity is maintained at 3.7m. 3 / (t·h), in conjunction with 360m 3 The bottom blowing flow rate is / h. The combined top and bottom strong stirring enhances the heating of the molten pool and the rapid melting of scrap steel, avoiding the problem of low-temperature slag overflow in the early stage under low iron ratio conditions. The model synchronously collects the carbon monoxide volume concentration of the flue gas at the furnace mouth in real time. When the carbon monoxide volume concentration is detected to be below 8% for 5 consecutive seconds, the top blowing oxygen lance is automatically raised temporarily by 150mm. When the carbon monoxide volume concentration rises back to above 12%, it is immediately restored to the 1400mm blowing lance position to avoid smelting abnormalities caused by carbon-oxygen reaction lag.

[0023] When the oxygen blowing step accuracy reaches 15%, the automatic steelmaking model raises the top-blown oxygen lance to the slag-forming lance position 1800mm above the molten pool surface, while simultaneously reducing the top-blown oxygen supply intensity to 3.2m. 3 / (t·h), reducing the consumption rate of ferrous oxide in the furnace and creating conditions for slag formation; simultaneously triggering the automatic feeding system, adding 600kg of coke at once, completing the precise addition of the heating agent.

[0024] (3) Perform mid-term slag smelting operations: Within the entire oxygen supply range of 15%-40%, the automated steelmaking model consistently maintained an oxygen supply intensity of 3.2m. 3 / (t·h), controlling the top-blown oxygen lance to gradually decrease linearly from the slag-forming lance position of 1800mm to the blowing lance position of 1400mm as the oxygen step increases, continuously accumulating ferrous oxide in the molten pool slag, promoting stable slag melting and dephosphorization reactions. Within this range, the model performs a slag-forming disturbance operation every 5% of the oxygen step, specifically: when the oxygen step reaches 20%, 25%, 30%, and 35% respectively, the top-blown oxygen lance is temporarily raised by 200mm, maintained for 1% of the oxygen step duration, and then returned to the preset lance position for the current stage, while the bottom-blown flow rate is temporarily increased to 300m³. 3 / h, starts and stops synchronously with the gun position adjustment, and breaks the abnormal foaming of slag through top and bottom joint disturbance, taking into account the slag-making effect and the requirements of preventing slag overflow and preventing dryness.

[0025] When the oxygen blowing step accuracy reaches 40%, the automatic steelmaking model will increase the top blowing oxygen supply intensity to 3.45m. 3 / (t·h), further enhancing the stirring intensity of the molten pool, while reducing the bottom-blown gas flow rate to 240m. 3 / h, completing the switch from mid-stage slag formation to late-stage enhanced mixing.

[0026] (4) Perform the final stage of temperature and carbon control operations: During the early-stage intensified stirring phase of the oxygen step (40%-80%), the automated steelmaking model maintained a constant stirring depth of 3.45m. 3 The third oxygen supply intensity (t·h) is gradually reduced as the oxygen step increases, with the top-blown oxygen lance position decreasing to continuously enhance molten pool stirring, promote complete melting of the remaining scrap steel, and ensure uniform temperature and composition of the molten pool. When the oxygen step precision reaches 80%, the model first lowers the top-blown oxygen lance to a position 1200mm above the molten pool surface, and then raises it to a position of 1300mm to perform a variable lance position slagging operation, completing the final slagging process.

[0027] After the final slag formation is completed, the final carbon extraction and temperature control stage begins. The automated steelmaking model lowers the top-blown oxygen lance to the carbon extraction lance position, 1000mm above the molten pool surface, while simultaneously reducing the top-blown oxygen supply intensity to 3.2m. 3 / (t·h), to achieve final slag viscosity and appropriately extend the blowing time to ensure accurate target temperature; simultaneously switch the bottom blowing gas flow rate back to 360m³ / h. 3 The bottom blowing gas supply medium is switched from nitrogen to argon to enhance the stirring of the final molten pool and ensure uniform steel composition and temperature. During this stage, the time for lowering the lance and removing carbon is strictly controlled to be no less than 60 seconds until the blowing process is terminated.

[0028] Ultimately, the entire blowing process in this embodiment lasted 14 minutes and 20 seconds, with a carbon extraction operation time of 72 seconds. The final steel temperature was 1645°C, and the steel composition was C: 0.06%, Si: 0.01%, Mn: 0.08%, P: 0.012%, and S: 0.025%. The double hit rate of the final temperature and composition reached 98.2%. There were no abnormal conditions such as ignition failure, slag overflow, splashing, or sticking to the lance throughout the process. It can stably adapt to the continuous production of the automatic steelmaking model under normal low iron ratio conditions.

[0029] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A low-iron-ratio smelting method suitable for automated steelmaking models, characterized in that, It includes four stages: initial blowing and ignition, early molten pool heating, mid-term slag formation and smelting, and final temperature and carbon control. The specific contents are as follows: Ignition and blowing stage: During the oxygen step of 0%-3%, ignition is carried out using the ignition gun position and the first oxygen supply intensity. After ignition, when the oxygen step reaches 3%, the oxygen gun is lowered to the blowing gun position and the first oxygen supply intensity is maintained. At the same time, the first bottom blowing flow rate is used, and the first batch of slag is added. In the early stage of molten pool heating: Before the oxygen step reaches 15%, maintain a low lance position and high oxygen supply intensity. When the oxygen step reaches 15%, raise the oxygen lance to the slag-forming lance position and adopt the second oxygen supply intensity, while adding all the coke. Mid-term slag smelting stage: During the oxygen step of 15%-40%, the second oxygen supply intensity is continuously used, and the oxygen lance is gradually reduced to the open blowing position. When the oxygen step reaches 40%, the third oxygen supply intensity is switched and the second bottom blowing flow rate is used. Final temperature and carbon control stage: When the oxygen step reaches 80%, the slag-forming operation is carried out by changing the lance position. After the slag-forming is completed, the oxygen lance is lowered to the carbon-pulling lance position and the fourth oxygen supply intensity is adopted. At the same time, the first bottom blowing flow rate is switched to perform the final carbon-pulling operation.

2. The low-iron-ratio smelting method suitable for automated steelmaking models according to claim 1, characterized in that, The specific heights of the different lance positions are as follows: the ignition lance position is 2200mm above the liquid surface; the blowing lance position is 1400mm above the liquid surface; the slag-forming lance position is 1800mm above the liquid surface; the carbon-pulling lance position is 1000mm above the liquid surface; the slag-forming operation with different lance positions is as follows: first lower the oxygen lance to a position 1200mm above the liquid surface, and then raise it to a position 1300mm above the liquid surface.

3. A low-iron-ratio smelting method suitable for automated steelmaking models according to claim 2, characterized in that, The initial oxygen supply intensity is 3.7m. 3 / t·h, the second oxygen supply intensity is 3.2m 3 / t·h, the third oxygen supply intensity is 3.45m 3 / t·h, the fourth oxygen supply intensity is 3.2m 3 / t·h; the first bottom blowing flow rate is 360m³ / t·h. 3 / h, the second bottom blowing flow rate is 240m³ / h. 3 / h.

4. A low-iron-ratio smelting method suitable for automated steelmaking models according to claim 3, characterized in that, During the initial ignition phase, the first batch of slag is added in batches. When the oxygen level reaches 3%, 40% of the total amount of lime and 50% of the total amount of magnesium balls are added. When the oxygen level reaches 8%, 30% of the total amount of lime is added.

5. A low-iron-ratio smelting method suitable for automated steelmaking models according to claim 4, characterized in that, During the intermediate slag-forming smelting stage, when the oxygen step rate is between 15% and 40%, a slag-forming disturbance operation is performed every 5% of the oxygen step rate. Specifically, the top-blown oxygen lance position is temporarily raised by 200mm, maintained for 1% of the oxygen step rate, and then returned to the original position. At the same time, the bottom-blown flow rate is temporarily increased to 300m³. 3 / h, starts and stops synchronously with the gun position adjustment.

6. A low-iron-ratio smelting method suitable for automated steelmaking models according to claim 5, characterized in that, During the final temperature and carbon control stage, the operation time of lowering the lance and pulling carbon is controlled to ≥60s, and the molten pool is continuously stirred until the blowing is terminated.

7. A low-iron-ratio smelting method suitable for automated steelmaking models according to claim 6, characterized in that, During the final temperature and carbon control stage, when the oxygen concentration is between 80% and 100%, the composition of the flue gas at the furnace mouth is monitored in real time to detect the ferrous oxide mass fraction in the molten pool slag. When the detected ferrous oxide mass fraction is <15%, the top-blown oxygen lance position is raised by 100mm. The original position is restored when the ferrous oxide mass fraction returns to the 15%-20% range. When the ferrous oxide mass fraction is higher than 20%, the top-blown oxygen supply intensity is increased by 0.1m. 3 / (t·h), when the ferrous oxide mass fraction falls back to the target range, restore the original oxygen supply intensity.

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