Method for calculating and controlling thickness of slag layer of continuous casting tundish

Abstract

The invention relates to a method for calculating and controlling the thickness of a slag layer of a continuous casting tundish, and the method comprises the following steps: 1, building a slag former slag production quantity prediction model, 2, building a large ladle casting slag quantity prediction model, 3, estimating the slag quantity under abnormal conditions, 4, meeting the thickness requirements of slag layers of different steel grades, 5, calculating the thickness H of the slag layer, 6, calculating the thickness H of the slag layer, and 7, calculating the thickness H of the slag layer. And 6, optimizing the estimation model.

Description

Technical Field

[0001] The present invention relates to a method, specifically to a method for calculating and controlling the thickness of the slag layer in a continuous casting tundish, belonging to the technical field of estimating the thickness of the slag layer in the continuous casting process of iron and steel enterprises. Background Art

[0002] Meishan Steelworks has 4 sets of continuous casting machines. Each set of continuous casting machine is equipped with 1 tundish, and 2 crystallizers are arranged under each tundish to realize the simultaneous casting of slab billets on 2 production lines. The main function of the tundish is to store molten steel to achieve continuous casting during ladle change. Since the tundish is an open-top container, on the one hand, it is to avoid adverse chemical reactions when molten steel contacts air and reduce the quality of molten steel. On the other hand, it is to avoid rapid heat dissipation of molten steel, large temperature drop, and easy occurrence of problems such as cold steel blockage. To solve the above two problems, slag-making operations need to be carried out on the continuous casting tundish. The main slag-making raw materials are rice balls and covering agents added by robots.

[0003] How to control the thickness of the slag layer has always been a headache problem on site. Due to the harsh on-site environment and limited space, there is no electronic means for measuring the thickness of the slag layer. Operators insert the oxygen lance vertically into the tundish and wait for a certain time to pull it out. Since the temperature difference between the slag layer and the molten steel is large, the temperature of the oxygen lance in the slag layer is significantly lower than the length of the oxygen lance in the molten steel. The length of the oxygen lance in the slag layer is the thickness of the slag layer. This measurement method is not timely and continuous, the accuracy cannot be guaranteed, and the operation is dangerous.

[0004] The control of the slag layer thickness has a great influence on continuous casting. If the slag layer is too thin, problems such as overoxidation of molten steel composition, large loss of molten steel temperature, and reduction of molten steel purity are likely to occur. If the slag layer is too thick, problems such as slag entrainment during molten steel casting are likely to occur, affecting the quality of slab billets and increasing the casting cost. Therefore, reasonably controlling the thickness of the slag layer is the key to ensuring the quality of continuous casting.

[0005] In this patent, during a tundish casting cycle (continuous casting of multiple furnaces), the sources of the slag content in the tundish are traced and statistically analyzed, and a dynamic calculation model is established in combination with the different requirements of different steel grades for the slag layer and the process parameters in the production process. The accuracy of the model estimation results is verified by the actual measurement method of the oxygen lance, and the model is corrected by continuously optimizing the parameters to achieve the purpose of accurate calculation and applying it to production.

[0006] Description of the comparison result with the literature closest to the content of this patent application:

[0007] Literature 1: Method and device for measuring the thickness of the slag in the continuous casting tundish of a continuous casting machine, CN201510149593.2

[0008] It discloses a method and device for measuring the thickness of the slag in the tundish of a continuous casting machine. The thickness measurement method includes: a winding step, a measurement step, and a thickness determination step. The thickness measurement device includes: a support frame, a first metal wire, and a second metal wire; the support frame is rod-shaped and has a clamping portion and an insertion portion in the vertically downward axial direction; the first metal wire and the second metal wire are wound on the insertion portion, and the first metal wire and the second metal wire form an overlapping area on the insertion portion; wherein, the melting points of the first metal wire and the second metal wire are 1400°C to 1500°C and 1000°C to 1100°C respectively. Through the above technical solution, the present invention realizes that the thickness measurement device has a simple structure, is easy to operate, has a short measurement time, low cost, and high measurement accuracy for the slag thickness in the tundish of the continuous casting machine.

[0009] This document is a complete physical device detection method, which uses a support frame, a first metal wire, a second metal wire, etc., and calculates based on the melting points of the first metal wire and the second metal wire.

[0010] Document 2: Method for Measuring the Slag Quantity in the Continuous Casting Tundish CN201910636570.2,

[0011] The present invention discloses a method for measuring the slag quantity in the continuous casting tundish. This method is realized based on a measuring device for the slag quantity in the continuous casting tundish. The measuring device includes a ladle turret pressure head (4), a ladle weight detector (5), a steel slag detector (6), a nozzle opening detector (7), a tundish weight detector (8), a process signal interface unit (9), and a data processing and calculation module (10); the measuring method includes the following steps: Step 1: Calibrate the slag-making density ρ_C of the covering agent, the steel slag density ρ_g of the ladle, and the slag quantity S_R flowing into the mold; Step 2: Calculate the total slag quantity S of the tundish (3) through the data processing and calculation module (10); Step 3: Perform deviation correction on the total slag quantity S through the self-correction coefficient E.

[0012] This document is for off-line measurement after the event and is an experimental non-production method. See Step 1.11: In the continuous casting plan of the steel grade, after the casting is completed and the molten steel is emptied, when only steel slag remains in the tundish (3), the weight of the tundish detected by the tundish weight detector (8) at this time is considered the weight of the steel slag Wcr in the tundish; Step 1.21: After a continuous casting plan is completed, measure the weight of the steel slag Wy in the mold and the weight of the covering agent input into the mold Wyc, and take the weight of the steel slag Wy in the mold minus the weight of the covering agent input into the mold Wyc as the weight of the steel slag flowing into the mold.

[0013] The difference of the present invention lies in that during the casting period of one tundish, the types and weights of slag-making agents added are cumulatively calculated in real time online, and are respectively multiplied by the slag-making coefficients related to the types to estimate the slag production amount of the slag-making agents. At the same time, according to the molten steel yield of the corresponding unit every day, the slag amount flowing into the tundish during each ladle casting is calculated and cumulated, and the slag layer thickness of the tundish is dynamically estimated according to the cumulative result. And the accuracy of the estimation result is verified by using the on-site measurement method, and the estimation model is optimized until the purpose of accurately predicting the slag layer thickness is achieved. Summary of the Invention

[0014] The present invention aims at the problems existing in the prior art and provides a method for calculating and controlling the slag layer thickness of a continuous casting tundish. The present invention relates to a method for calculating the slag layer thickness of a continuous casting tundish, which determines the source of the slag content in the tundish and conducts tracking and statistics. By cumulatively calculating the types and weights of slag-making agents added during one tundish casting period, a dynamic calculation model is established corresponding to the slag-making coefficients related to the types to calculate the slag production amount of the slag-making agents. A dynamic calculation model is established, and at the same time, according to the molten steel yield of the corresponding unit, the slag amount flowing into the tundish during each ladle casting is calculated and cumulated, and the slag layer thickness of the tundish is dynamically estimated according to the cumulative result. And the accuracy of the estimation result is verified by using the on-site measurement method, and the estimation model is optimized until the purpose of accurately predicting the slag layer thickness is achieved.

[0015] A method for calculating and controlling the slag layer thickness of a continuous casting tundish, the method comprising the following steps:

[0016] Step 1: Establish a prediction model for the slag production amount of the slag-making agent

[0017] 1. Establish an array SW[k] of the single addition amount of the slag-making agent, an array TW[k] of the cumulative addition amount of the slag-making agent, and an array N[k] of the slag-making coefficients of different types of slag-making agents, (k = 0, 1, 2..., for example, k = 0 represents rice balls; k = 1 represents the slag-making agent; K = 2 represents other types of slag-making agents). SW[k] comes from the measurement of the slag-making agent adding device (such as a robot, etc.), and the k type definition and N[k] come from the slag-making agent process system manual.

[0018] 2. Establish a calculation formula for the slag production amount of the slag-making agent, and record the slag production amounts of all different types of slag-making agents as Q1.

[0019] The slag production amount Q1 = ∑TW[k]*N[k], such as TW[0]*N[0]+TW[1]*N[1]+TW[2]*N[2],

[0020] The cumulative amount of the slag-making agent TW[k] = TW[k]+SW[k],

[0021] When the tundish is put into production at the start of casting, Q1 = 0, SW[k] = 0, and TW[k] = 0.

[0022] Step 2: Establish a prediction model for the slag volume during tundish pouring

[0023] Record the slag volume formed in the tundish after the ladle steel is poured as Q2.

[0024] Record the single-time slag volume during ladle pouring as SQ1, and SQ1 comes from the ladle slagging device.

[0025] Q2 = Q2 + SQ1

[0026] When the tundish is put into production, Q2 = 0 and SQ1 = 0.

[0027] Step 3: Estimate the slag volume in case of abnormality

[0028] Record the estimated slag volume in case of abnormality as SQ2[k], and SQ2[k] comes from manual calculation.

[0029] Record the cumulative value of the estimated slag volume in case of abnormality as Q3

[0030] Q3 = Q3 + ∑SQ2[k] * N[k]

[0031] The estimation of the slag volume in case of abnormality includes but is not limited to abnormal slagging during ladle pouring, manual addition of rice balls, slag formers, etc. by the robot feeding system when it is abnormal and the slag increment cannot be automatically calculated.

[0032] Step 4: Requirements for the slag layer thickness of different steel grades

[0033] Determine the optimal slag layer thickness H1 required for different steel grades according to the on-site experience.

[0034]

[0035] Step 5: Calculate the slag layer thickness H

[0036] Record the total slag volume in the tundish as Q,

[0037] The slag density σ1, determined by experiment

[0038] Record the cross-sectional area of the tundish as S, the designed measured value

[0039] Record the calculated slag layer thickness as H

[0040] Q = Q1 + Q2 + Q3

[0041] H = Q ÷ σ1 ÷ S

[0042] By comparing the calculated slag layer thickness H with the optimal slag layer thickness H1 required for the steel grade, set △H as the process slag layer deviation limit value, and △H > 0. The slag layer thickness control curve is as follows:

[0043] |H - H1| < △H (holding area), that is, the thickness of the slag layer is within a reasonable range and no treatment is required.

[0044] H > H1 + △H (slag overflow area), that is, the thickness of the slag layer exceeds the required thickness, and slag overflow treatment is required.

[0045] H < H1 - △H (slag making area), that is, when the thickness of the slag layer is less than the required thickness, rice balls, slag making agents, etc. need to be added for slag making. The amount of slag making agent to be added is denoted as Q4, and the calculation is as follows

[0046] Q4 = |H - H1| * s * σ1 ÷ N [k]

[0047] Step 6: Estimation model optimization

[0048] In the initial stage of model input, due to certain deviations in the slag making coefficients N [k], slag density σ1, tundish cross-sectional area S, and the amount of slag flowing into the tundish at the end of each ladle pouring, the estimation parameters need to be optimized to achieve the purpose of consistency between the actual measurement and the model estimation. Regularly measure the thickness of the slag layer (such as using the robot of the slag making agent adding device) and compare it with the model estimation value to correct the calculated thickness H of the slag layer.

[0049] Use the robot of the slag making agent adding device to measure the thickness H2 of the slag layer. If H2 << H1 - △H or H2 > H1 + △H, take H = H2.

[0050] Compared with the prior art, the present invention has the following advantages: 1. During a tundish pouring period, it can calculate and control the thickness of the slag layer online in real time, realizing dynamic control of the accuracy of the slag layer thickness and improving the quality of molten steel; 2. In the case of continuous casting of multiple furnaces in the tundish, considering all types of slag making agents used comprehensively, tracking and calculating the important sources of the slag content in the tundish, reasonably controlling the use of slag making agents and reducing the consumption cost; 3. It is a dynamic calculation and control model, which can automatically optimize the model through process parameter correction and actual measurement verification, and correct the model by continuously optimizing parameters to improve the accuracy of the calculation results; 4. It provides a large amount of data basis for studying the relationship between the slag layer and the quality of steel grades, and is an important part of improving the intelligent means of continuous casting. Brief description of the drawings

[0051] Figure 1 It is a schematic diagram of the positions of the ladle, tundish, and mold;

[0052] Figure 2 It is a control curve of the slag layer thickness;

[0053] Figure 3 It is a flow chart of model estimation.

[0054] In the figure: 1. Slag addition hole, 2. Slag layer, 3. Slag overflow port, 4. Middle tundish section, 5. Molten steel. Detailed implementation mode

[0055] To deepen the understanding of the present invention, the following detailed description is given to this embodiment with reference to the accompanying drawings.

[0056] Embodiment 1: Taking the casting of high-carbon steel and slag formers (k = 0, 1, 2) as an example, the method includes the following steps:

[0057] The first step: Establish a prediction model for the slag production of the slag former,

[0058] Specifically as follows:

[0059] 1. Establish an array SW[k] for the single addition amount of the slag former, an array TW[k] for the cumulative addition amount of the slag former, and an array N[k] for the slag formation coefficients of different types of slag formers (take k = 0, 1, 2).

[0060] 2. Establish a calculation formula for the slag production of the slag former, and record the slag production of all different types of slag formers as Q1.

[0061] Q1 = ∑TW[k]*N[k] = TW[0]*N[0] + TW[1]*N[1] + TW[2]*N[2],

[0062] TW[0] = TW[0] + SW[0], TW[1] = TW[1] + SW[1], TW[2] = TW[2] + SW[2],

[0063] When the tundish is on line at the start of casting, Q1 = 0, SW[k] = 0, TW[K] = 0, N[0] = 0.2,

[0064] Slag former process system manual: Set N[0] = 0.5, N[0] = 0.8, N[0] = 0.6.

[0065] As of the current TW[0] = 200kg, TW[1] = 500kg, TW[2] = 200kg

[0066] Q1 = 200*0.5 + 500*0.8 + 200*0.6 = 620kg

[0067] The second step: Establish a prediction model for the slag volume poured from the ladle

[0068] Record the slag volume formed in the tundish after pouring the ladle molten steel as Q2.

[0069] Record the single slag volume poured from the ladle as SQ1. SQ1 comes from the slag discharged from the ladle slag discharge device for each ladle, about 20kg. After continuously casting 5 ladles of molten steel:

[0070] Q2 = Q2 + SQ1 = 18x5 = 90kg

[0071] When the tundish is put into operation, Q2 = 0 and SQ1 = 0.

[0072] Step 3: Slag volume estimation under abnormal conditions

[0073] The slag volume estimation under abnormal conditions is denoted as SQ2[K], and SQ2[K] comes from manual calculation.

[0074] The cumulative value of the slag volume estimation under abnormal conditions is denoted as Q3: Suppose that up to the current manual SQ2[0] = 80 kg, SQ2[1] = 100 kg, SQ2[2] = 0 kg,

[0075] Q3 = Q3 + ∑SQ2[k]*N[k] = Q3 + SQ2[0]*N[0] + SQ2[1]*N[1] + SQ2[2]*N[2] = 80*0.5 + 100*0.8 = 120 kg

[0076] Step 4: Requirements for slag layer thickness of different steel grades

[0077] According to the on-site experience in the process system manual, determine the required slag layer thickness H1 for different steel grades.

[0078]

[0079] Step 5: Calculate the slag layer thickness

[0080] The total slag volume in the tundish is denoted as Q,

[0081] The slag density σ1 is determined by experiment

[0082] The cross-sectional area of the tundish is denoted as S, and it is set that S = 8 m 2 、σ1 = 1 g / ml

[0083] The calculated slag layer thickness is denoted as H,

[0084] Q = Q1 + Q2 + Q3 = 620 + 90 + 120 = 830 kg

[0085] H = Q ÷ σ1 ÷ S = 830 ÷ 1 ÷ 6 = 103.7 mm

[0086] By comparing the calculated slag layer thickness H with the required slag layer thickness H1 of the steel grade, △H1 is the process slag layer deviation limit value = 5 mm, and △H1 > 0:

[0087] |H - H1| = 103.7 - 100 = 3.37 mm = <△H = 5 mm, that is, 95 mm < H < 105 mm, and the slag layer thickness remains within a reasonable range and does not need to be treated.

[0088] Step 6: Optimization of the estimation model

[0089] Optimize the estimated parameters to achieve the purpose of consistent actual measurement and model estimation, and regularly test the slag layer thickness (such as using the robot of the slag-making agent adding device) and compare it with the model estimated value to correct the calculated slag layer thickness H.

[0090] Use the robot of the slag-making agent adding device to test the slag layer thickness H2. If H2 < 95 mm or H2 > 105 mm, take H = H2.

[0091] It should be noted that the above embodiments are not used to limit the protection scope of the present invention. Equivalent transformations or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A method for calculating and controlling the slag layer thickness of a continuous casting tundish, characterized in that, the method comprises the following steps: The first step: Establish a prediction model for the slag production of the slag former, The second step: Establish a prediction model for the slag volume flowing into the tundish during the ladle pouring, The third step: Estimate the slag volume under abnormal conditions, The fourth step: Requirements for the slag layer thickness of different steel grades, The fifth step: Calculate the slag layer thickness H, The sixth step: Optimize the estimation model.

2. The method for calculating and controlling the slag layer thickness of a continuous casting tundish according to claim 1, characterized in that, The first step: Establish a prediction model for the slag production of the slag former, 1. Establish an array SW[k] of the single addition amount of the slag former, an array TW[k] of the cumulative addition amount of the slag former, and an array N[k] of the slag formation coefficients of different types of slag formers, (k = 0, 1, 2..., for example, k = 0 represents rice balls; k = 1 represents the slag former; k = 2 represents other types of slag formers), SW[k] comes from the metering of the slag former addition device, the definition of the k type, and N[k] comes from the slag former process system manual, 2. Establish a calculation formula for the slag production of the slag former, and record the slag production of all different types of slag formers as Q1, The slag production Q1 = ∑TW[k]*N[k], such as TW[0]*N[0]+TW[1]*N[1]+TW[2]*N[2], The cumulative amount of the slag former TW[k] = TW[k]+SW[k], When the tundish is put into operation at the start of casting, Q1 = 0, SW[k] = 0, and TW[k] = 0.

3. The method for calculating and controlling the slag layer thickness of a continuous casting tundish according to claim 2, characterized in that, The second step: Establish a prediction model for the slag volume flowing into the tundish during the ladle pouring, specifically as follows: Record the slag volume flowing into the tundish after the ladle molten steel is poured as Q2, Record the single slag volume flowing into the tundish during the ladle pouring as SQ1, and SQ1 comes from the ladle slagging device, Q2 = Q2+SQ1; When the tundish is put into operation, Q2 = 0 and SQ1 = 0.

4. The method for calculating and controlling the slag layer thickness of a continuous casting tundish according to claim 3, characterized in that, The third step: Estimate the slag volume under abnormal conditions, specifically as follows: The estimated slag volume under abnormal conditions is recorded as SQ2[k], and SQ2[k] comes from manual calculation, The cumulative value of the estimated slag volume under abnormal conditions is recorded as Q3, Q3 = Q3+∑SQ2[k]*N[k] The estimation of the slag volume under abnormal conditions includes but is not limited to abnormal slag flowing during ladle pouring, manual addition of rice balls, slag formers, etc. by the robot feeding system when the slag increment cannot be automatically calculated.

5. The method for calculating and controlling the slag layer thickness of a continuous casting tundish according to claim 3 or 4, characterized in that, The fourth step: Requirements for the slag layer thickness of different steel grades, specifically as follows: Determine the optimal slag layer thickness H1 required for different steel grades, 6. The method for calculating and controlling the slag layer thickness of a continuous casting tundish according to claim 5, characterized in that, The fifth step: Calculate the slag layer thickness H, specifically as follows: Record the total slag volume in the tundish as Q, The slag density σ1, determined by experiment Record the cross-sectional area of the tundish as S, the designed measured value Record the calculated slag layer thickness as H, Q = Q1+Q2+Q3, H = Q÷σ1÷S, By comparing the calculated slag layer thickness H with the optimal slag layer thickness H1 required for the steel grade, △H is set as the process slag layer deviation limit value, and △H>0. The slag layer thickness control curve is as follows: |H - H1| < △H (holding area), that is, the slag layer thickness is within a reasonable range and no treatment is required. H > H1 + △H (slag overflow area), that is, the slag layer thickness exceeds the required thickness and slag overflow treatment is required. H < H1 - △H (slag making area), that is, if the slag layer thickness is less than the required thickness, rice balls, slag making agents, etc. need to be added for slag making. The amount of slag making agent to be added is denoted as Q4, and the calculation is as follows Q4 = |H - H1| * s * σ1 ÷ N [k].

7. The method for calculating and controlling the slag layer thickness of the continuous casting tundish according to claim 6, characterized in that Step 6, optimize the estimation model, specifically as follows: In the initial stage of model input, due to certain deviations in the slag making coefficients N [k], slag density σ1, tundish cross-sectional area S, and the amount of slag flowing into the tundish at the end of each ladle pouring, it is necessary to optimize the estimation parameters to achieve the purpose of consistency between the actual measurement and the model estimation. Regularly measure the slag layer thickness (such as using the robot of the slag making agent adding device) and compare it with the model estimation value to correct the calculated slag layer thickness H. Use the robot of the slag making agent adding device to measure the slag layer thickness H2. If H2 << H1 - △H or H2 > H1 + △H, take H = H2.

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