Ladle bottom blowing device and ladle bottom blowing flow control and regulation method

Abstract

The application discloses a ladle bottom blowing device and a ladle bottom blowing flow control and regulation method. The ladle bottom blowing device comprises a gas permeable element, the bottom of the gas permeable element is connected with a gas storage chamber, the gas permeable element is composed of a gas permeable brick made of refractory material and an outer steel shell, and the gas permeable brick has a plurality of uniformly distributed gas permeable channels which are vertically permeable. The gas storage chamber is composed of a gas storage cavity and a gas inlet pipeline, and the gas permeable channels are communicated with the gas storage cavity. The ladle bottom blowing flow control and regulation method comprises the following steps: bottom blowing data acquisition, bottom blowing data processing, correction of a proportional coefficient, determination of a fault level, taking countermeasures, and adjustment of the bottom blowing flow. The application solves the technical problems of unreasonable setting of the ladle bottom blowing flow and insufficient stirring of the molten pool, which leads to the decline of product quality.

Description

Technical Field

[0001] This invention relates to a bottom blowing device for a ladle and a method for controlling and adjusting the bottom blowing flow rate of a ladle, belonging to the field of ladle furnace refining technology. Background Technology

[0002] In the steel manufacturing process, ladle refining is an important smelting method. Bottom blowing of argon into the ladle introduces argon gas from the bottom of the ladle into the molten steel. This process has the functions of uniformizing the composition and temperature of the molten steel, promoting the transport of solutes in the molten steel, and removing inclusions in the steel. It is a major technical means to improve the cleanliness of molten steel and improve product quality.

[0003] Existing bottom-blowing technology for steel ladles utilizes permeable bricks to introduce a gaseous medium into molten steel. Traditional permeable brick gas jets have a limited stirring range in the molten steel, resulting in insufficient agitation of the molten pool. This presents several disadvantages, including hindering the uniformity of molten steel composition and temperature, and the removal of inclusions. Furthermore, the concentrated vertical argon jets exert a strong impact on the slag layer on the molten steel surface, leading to problems such as exposed molten steel oxidation contamination and slag entrapment. Simultaneously, the bottom-blowing flow rate adjustment in current technologies is mostly determined manually based on experience. The bottom-blowing control process is relatively simple and cannot effectively address abnormal situations such as blockages and leaks. This easily leads to problems such as slag entrapment, insufficient bottom-blowing, and uneven agitation of the molten pool, ultimately causing fluctuations in molten steel quality and resulting in reduced product quality. For example, patent document CN107739778A discloses a ladle bottom blowing argon device and its refining stirring method. This document specifically discloses a ladle bottom blowing permeable brick with multiple gas outlet rings and a control method. By applying different flow rates to different permeable rings, the bottom blowing stirring effect can be improved. However, this technology requires the use of a special ladle, and the permeable brick has a complex structure, high cost, low versatility, and certain difficulties in implementation. Summary of the Invention

[0004] The purpose of this invention is to provide a well-designed, highly accurate, and easily operable ladle bottom blowing device and a ladle bottom blowing flow control and adjustment method, thereby solving the technical problems of unreasonable ladle bottom blowing flow setting and insufficient molten pool stirring leading to product quality degradation in the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A bottom-blowing device for a steel ladle includes a venting element with a gas storage chamber connected to its bottom. Specifically, the venting element and the gas storage chamber are connected by flange bolts. The venting element consists of refractory permeable bricks and an outer steel shell. The refractory permeable bricks have several permeable channels that are open from top to bottom and are generally evenly distributed. The gas storage chamber consists of a gas storage cavity and an air inlet pipe, and the venting channels communicate with the gas storage cavity.

[0007] The refractory permeable brick is frustum-shaped, and the upper base diameter Φ of the refractory permeable brick is...top =50mm~150mm, bottom diameter Φ bottom =100mm~200mm, height H=200mm~600mm. The thickness of the outer steel shell σ=0.5mm~5.0mm.

[0008] The ventilation channels are distributed in a centrally divergent pattern (e.g., ...). Figure 1-6 As shown, the cross-section of the ventilation channel is circular or rectangular. When the ventilation channel is circular, its diameter Φ = 0.5mm to 1.5mm; when the ventilation channel is rectangular, its width d = 0.5mm to 3.0mm and its length D = 5.0mm to 40mm. The number of ventilation channels is greater than 20.

[0009] The ventilation channel extends from the bottom of the ventilation brick outwards to the top of the ventilation brick, and the included angle θ between the ventilation channel and the bottom surface of the refractory ventilation brick is: 80°≤θ<90°.

[0010] The specific steps for controlling and adjusting the bottom blowing flow rate of the ladle are as follows:

[0011] Step 1: Bottom blowing data acquisition and processing; Step 1, bottom blowing data acquisition, refers to the start of the bottom blowing process in the ladle, where the maximum bottom blowing argon flow rate Q is activated. max The actual stable argon flow rate Q after collecting data for time Δt. sta Where: 0NL (standard liters) / min / t < Q max ≤7.5NL / min / t,0.5min<Δt≤3.0min,0NL / min / t<Q sta ≤Q max ;

[0012] Step 1, bottom blowing data processing, refers to processing the actual stable argon flow rate Q according to equation (1). sta Divide by the maximum argon flow rate Q max The proportionality constant k is obtained as follows:

[0013]

[0014] Step 2: Correct the proportional coefficient, determine the fault level, and take countermeasures; Step 2, correcting the proportional coefficient and determining the fault level, refers to obtaining the correction coefficient λ for the proportional coefficient k according to the table below, and providing the corresponding fault level and troubleshooting measures:

[0015] Table 1 Correction Factors and Reference Fault Types

[0016]

[0017]

[0018] The specific countermeasures taken in step 2 are shown in the table below:

[0019] Table 2 Specific Implementation Methods of Countermeasures

[0020]

[0021] When 1.50 ≤ k, smelting stops, which can be understood as λ being 0.

[0022] Step 3: Adjust the bottom blowing flow rate:

[0023] Step 3, adjusting the bottom blowing flow rate, refers to adjusting the original preset bottom blowing flow rate Q1 to the bottom blowing flow rate Q2 according to equation (2) at each argon blowing smelting stage, based on the proportional coefficient k and the corresponding correction coefficient λ.

[0024] Q2=λ·Q1 (2)

[0025] Traditional permeable bricks have a limited argon gas coverage area, resulting in uneven stirring of the molten pool. Furthermore, the vertical argon jet increases the risk of exposed steel oxidation contamination and slag entrapment. Additionally, bottom blowing flow control relies solely on manual experience, leading to numerous inconsistencies in flow rate settings and an inability to effectively address issues such as blockage and leakage in the permeable bricks. This ultimately causes slag entrapment and incomplete bottom blowing, resulting in fluctuations in steel quality and a decline in product quality. This invention improves the permeability channel structure of the permeable brick by designing a centrally divergent permeable brick. The centrally divergent jet increases the horizontal velocity component of the argon gas, expanding the argon stirring range, improving steel stirring efficiency, and mitigating the concentrated impact of argon on the slag surface. This effectively avoids steel contamination caused by exposed steel molten steel absorbing gas and slag entrapment.

[0026] Currently, controlling the bottom blowing flow rate relies solely on manual operation experience, which is insufficient to effectively address abnormal situations such as blockage and leakage of the permeable bricks. Improperly set bottom blowing flow rates can ultimately lead to problems such as slag entrainment, incomplete bottom blowing, and weak argon stirring, thus reducing billet quality. This invention proposes a method for controlling and adjusting the bottom blowing flow rate of a ladle. It provides specific operating methods and corresponding measures for abnormal bottom blowing situations. The process is simple to implement, low-cost, and highly effective, effectively solving the technical problems of product quality degradation caused by improper ladle bottom blowing flow rate settings and insufficient molten pool stirring. Attached Figure Description

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] Figure 1 Front view of a centrally radiating circular hole bottom blowing device for steel ladles.

[0029] Figure 2 Cross-sectional structural diagram of a centrally radiating circular hole bottom blowing device for steel ladles.

[0030] Figure 3 A top view of a centrally radiating circular hole bottom blowing device for a steel ladle.

[0031] Figure 4 Front view of a centrally radiating slit ladle bottom blowing device.

[0032] Figure 5 Cross-sectional structural diagram of a center-radiating narrow slot ladle bottom blowing device.

[0033] Figure 6 Top view of a centrally radiating narrow slot ladle bottom blowing device.

[0034] Figure 7 This diagram illustrates insufficient stirring of the molten pool in the existing process.

[0035] Figure 8 This diagram illustrates the thorough stirring of the molten pool in this invention.

[0036] Figure 9 This is a comparison chart of product cleanliness.

[0037] Figure 10 This is a schematic diagram of a common bottom blowing device for steel ladles.

[0038] Figure 11 This is a schematic diagram of the bottom blowing device for the ladle of the present invention. Detailed Implementation

[0039] A center-diverging circular-hole ladle bottom-blowing device for improving the ladle bottom-blowing effect, structure as follows: Figures 1-3 As shown, the device includes a permeable element, which is connected to the gas storage chamber by flange bolts. The permeable element consists of a refractory permeable brick 1 and an outer steel shell 2. The refractory permeable brick 1 has several permeable channels 3 inside, which are evenly distributed on the refractory permeable brick. The gas storage chamber consists of a gas storage cavity 4 and an air inlet pipe 5. Specifically, the refractory permeable brick 1 is frustum-shaped, and the upper bottom diameter Φ of the refractory permeable brick 1 is... top =50mm~150mm, bottom diameter Φ bottom =100mm~200mm, height H=200mm~600mm. The thickness of the outer steel shell σ=0.5mm~5.0mm. Among them, the cross-section of the ventilation channel is circular with a diameter Φ=1.2mm, the number of ventilation channels n=64, the angle θ between the ventilation channel and the bottom of the ventilation brick is 88°, and the thickness of the outer steel shell 2 σ=1.5mm.

[0040] A high-end wire rod requires high cleanliness of molten steel, and its smelting process is BOF-LF-CC. LF refining employs a double-hole ladle bottom-blowing argon system to agitate the molten steel and remove inclusions. The bottom-blowing utilizes a centrally divergent slit (i.e., rectangular cross-section of the ventilation channel) ladle bottom-blowing device to improve the ladle bottom-blowing effect, as shown in the diagram. Figures 4-6As shown, the structure is the same as above, wherein the cross-section of the ventilation channel is rectangular, the width of the rectangular ventilation channel d = 1.0 mm, the length of the rectangular ventilation channel D = 20 mm, the number of ventilation channels n = 24, the angle between the ventilation channel and the bottom of the ventilation brick θ = 87°, and the thickness of the outer steel shell 2 σ = 1.5 mm.

[0041] The following steps are used to control the bottom blowing flow rate:

[0042] Step 1: During the LF feed of a certain furnace, start the maximum bottom blowing Q. max =800NL·min -1 Select Δt = 2 min, and the actual maximum flow rate Q of bottom blowing after 2 min is determined. sta =685NL·min -1 From the above, we can obtain the proportionality coefficient k = 0.86;

[0043] Step 2: Referring to Tables 1 and 2, determine the corresponding correction coefficient λ = 1.0 to 1.2 for this furnace run, which corresponds to the fault level of "minor blockage", and take appropriate measures.

[0044] Step 3: Adjust normal operation according to the correction factor:

[0045] Table 3 Original and Modified Bottom Blowing Flow Rates for a Certain Furnace

[0046]

[0047]

[0048] like Figure 10 The schematic diagram of a typical bottom-blowing ladle device shows that the argon gas flow direction is vertical, limiting the argon gas stirring range. Figure 11 As shown, the present invention increases the velocity component of argon gas in the horizontal direction by utilizing the centrally diverging jet through the gas permeable channel structure, thereby expanding the argon gas stirring range.

[0049] The bottom blowing flow rate can be adjusted in a timely manner according to the different operating conditions of each furnace. Figure 7 The original mixing process was used to achieve the desired mixing effect. Figure 8 The stirring effect of this heat is clearly visible. The original process resulted in weak stirring of the molten steel, a small stirring range, poor removal of inclusions, and exposed molten steel that was susceptible to oxidation and contamination by air, leading to low cleanliness. This new method effectively improves the bottom blowing stirring effect in the ladle, resulting in significant molten steel circulation, better removal of inclusions, and no exposed slag on the slag surface.

[0050] After smelting, the quantity and size of inclusions in the product are used as the criteria for judging product cleanliness. The lower the rate of inclusion exceeding the standard, the higher the product cleanliness and the better the quality. Figure 9As shown, after the implementation of this solution, with the improved stirring effect of molten steel, the removal effect of inclusions is better, the cleanliness of steel is significantly improved, the excess rate of inclusions in the final product is effectively controlled, and the product quality is significantly improved.

[0051] The above embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for controlling and adjusting the bottom blowing flow of a steel ladle, characterized in that the steel ladle is provided with a permeable element, the bottom of the permeable element is connected to a gas storage chamber, the permeable element is composed of a refractory permeable brick and an outer steel shell, the refractory permeable brick has several permeable channels that are open from top to bottom; the gas storage chamber is composed of a gas storage cavity and an air inlet pipe, and the permeable channels are connected to the gas storage cavity; The cross-section of the ventilation channel is circular or rectangular; The included angle θ between the air-permeable channel and the bottom surface of the refractory permeable brick is: 80°≤θ<90°; The ventilation channels are distributed in a centrally radiating pattern; The steps are as follows: Step 1, bottom blowing data acquisition and processing: 1.1 At the start of the bottom blowing process in the ladle, the maximum bottom blowing argon flow rate Qmax is activated, and the actual stable argon flow rate Qsta is collected after a time Δt, where: 0NL / min / t<Qmax ≤7.5NL / min / t, 0.5min<Δt≤3.0min, 0NL / min / t<Qsta ≤ Qmax; 1.2 Divide the actual stable argon flow rate Qsta by the maximum argon flow rate Qmax according to equation (1) to obtain the proportionality coefficient k: ， Step 2, determine the correction factor λ for the proportionality coefficient k: When 0 < k < 0.30, λ is taken as 1.5 to 2.

0. Fault type: severe blockage; Countermeasures: open the bottom blowing bypass for 3 to 8 minutes, then increase the bottom blowing flow rate, and if necessary, force the permeable bricks to be taken offline. When 0.30≤k<0.60, λ is taken as 1.2~1.5, the fault type is blockage; the countermeasures are to increase the bottom blowing flow rate and pressurize the smelting process. When 0.60≤k<0.90, λ takes a value of 1.0~1.2, the fault type is micro-blockage; the countermeasure is to increase the flow rate during smelting. When 0.90≤k<1.10, λ is 1.0, and the fault type is normal. When 1.10≤k<1.50, λ takes values ​​from 1.2 to 1.5, the fault type is micro-leakage, and the countermeasure is to increase the flow rate during smelting. When 1.50 ≤ k, λ is 0, the fault type is: gas leakage; the countermeasure is to stop smelting and immediately check the argon pipeline and the bottom blow joint of the ladle for gas leakage until the fault is eliminated. Step 3, adjust the bottom blowing flow rate Q2 according to formula (2): Q2 = λ·Q1 (2) Q1 is the original preset bottom blowing flow rate.

2. The ladle bottom blowing flow control and adjustment method according to claim 1, characterized in that: The ventilation channels are evenly distributed.

3. The ladle bottom blowing flow control and adjustment method according to claim 1, characterized in that: The refractory permeable brick is truncated cone-shaped.

4. The ladle bottom blowing flow control and adjustment method according to claim 3, characterized in that: The refractory permeable brick has an upper bottom diameter Φtop = 50mm~150mm, a lower bottom diameter Φbottom = 100mm~200mm, and a height H = 200mm~600mm.

5. The ladle bottom blowing flow control and adjustment method according to claim 1, characterized in that: The thickness of the outer steel shell is σ = 0.5mm to 5.0mm.

6. The ladle bottom blowing flow control and adjustment method according to claim 1, characterized in that: When the cross-section of the ventilation channel is circular, its diameter Φ = 0.5mm~1.5mm; when the cross-section of the ventilation channel is rectangular, its width d = 0.5mm~3.0mm and its length D = 5.0mm~40mm.

7. The ladle bottom blowing flow control and adjustment method according to claim 1, characterized in that: The number of ventilation channels is greater than 20.

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