Determination method for decarburization end point of RH automobile sheet

Abstract

The invention discloses an RH automobile sheet decarburization end point determination method. The method comprises the following steps: constructing a first decarburization determination model and a second decarburization determination model; wherein the first decarburization judgment model is a judgment method for predicting the carbon content through the vacuum degree change rate, the second decarburization judgment model is a judgment method for predicting the carbon content through characteristic value regression in the RH decarburization process, and through cooperation of the two methods, in the RH decarburization process, when the first decarburization judgment model judges that decarburization is finished, the first condition is met; when the second decarburization judgment model judges that the decarburization ending second condition is met, it is judged that the automobile sheet reaches the decarburization end point at the moment, decarburization is ended, and real-time online prediction of the decarburization end point of the automobile sheet is achieved. Compared with a traditional method for judging decarburization through manual sampling, the method can judge the decarburization end point without sampling, and the labor intensity is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of steel production, and in particular relates to a method for determining the decarburization endpoint of an RH automobile plate. Background Art

[0002] Zhanjiang Steel's automotive sheet requires a carbon content of ≤100ppm, but the carbon content after converter smelting is more than 300ppm, which cannot meet the carbon content requirements of automotive sheets. Therefore, automotive sheets need to undergo RH decarburization treatment.

[0003] During the RH treatment process, carbon and oxygen in the molten steel react to generate CO gas, which is removed, and the carbon content of the molten steel continues to decrease. When the carbon content of the molten steel reaches the target value, decarburization ends. In actual production, the carbon content of molten steel cannot be detected online. In order to determine whether the carbon content reaches the requirement, it is necessary to manually take steel samples for analysis, and determine the end point of automotive plate decarburization based on the analysis results.

[0004] The method of sampling to determine the end point of decarburization has two shortcomings. First, it takes 6-7 minutes from sampling to analysis, and data cannot be obtained in real time. During the process of waiting for the analysis of the steel sample, RH continues to decarburize, which easily leads to excessive decarburization and a long decarburization time. In addition, this method requires manual steel sampling, which is labor-intensive, and the molten steel temperature is as high as 1600℃. Manual sampling has operational risks. Summary of the invention

[0005] The invention provides a method for determining the decarburization endpoint of an RH automobile plate, which can improve the prediction accuracy.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solution: a method for determining the decarburization endpoint of RH automobile plate, characterized in that it comprises:

[0007] Construct the first decarburization judgment model for predicting the decarburization endpoint by vacuum degree change. According to the range of the carbon upper limit of the steel grade, set the critical vacuum degree, vacuum degree change rate critical value and change rate cumulative points for the model to start intervention judgment. During the RH decarburization process, the first decarburization judgment model calculates the vacuum degree change rate every 0.1-0.5min. When the actual vacuum degree is ≤ the vacuum degree critical value, the first decarburization model starts to intervene in the judgment. When the calculated vacuum degree change rate is ≤ the vacuum degree change rate critical value and the change rate cumulative points meet the set requirements, it is determined that the first condition for the end of decarburization is met.

[0008] The second decarburization judgment model is constructed by regression of process characteristic values ​​to predict carbon content. During the decarburization process, the characteristic values ​​affecting decarburization include the oxygen blowing amount V 1 , Decarburization time T 1 、The time T when the vacuum degree is ≤266pa 2 , scrap steel quantity M 1 、Aluminum addition amount M 2 、Toner quantity M3 and decarbonization final oxygen C 1 ; Based on historical data, the carbon content of molten steel W is obtained through big data regression C The relationship with the decarburization characteristic value is as follows:

[0009] W C =27.6+0.0111V 1 -0.0742T 1 +0.0454T 2 +0.00271M 1 +0.0349M 2 +0.0188M 3 -0.0228C 1 RH

[0010] During the decarburization process, the current characteristic value is read every 0.1-0.5 minutes to perform regression prediction on the carbon content; when the carbon content of the molten steel predicted by the second decarburization judgment model is ≤ the target carbon content, it is determined that the second condition for the end of decarburization is met;

[0011] In the RH decarburization process, when the first decarburization end condition and the second decarburization end condition are simultaneously met, it is determined that the automobile plate has reached the decarburization end point and the decarburization is ended.

[0012] Preferably, the first decarburization determination model calculates the vacuum degree change rate once every 0.2 minutes. The second decarburization determination model reads the current characteristic value once every 0.2 minutes to perform regression prediction on the carbon content.

[0013] The beneficial effect of the present invention is: by adopting the method of the present invention, a method of predicting carbon content by using vacuum degree change rate is combined with a method of predicting carbon content by regression of characteristic values ​​of RH decarburization process, and when both methods simultaneously predict the decarburization end point, decarburization is terminated, thereby realizing real-time online prediction of the decarburization end point of automobile plates.

[0014] Compared with the traditional method of determining decarburization by manual sampling, the method of the present invention can determine the decarburization endpoint without sampling, thereby greatly reducing labor intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0016] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0017] The present invention discloses a method for determining the decarburization endpoint of an RH automobile plate. The method combines a first decarburization determination model (a method for predicting carbon content by vacuum degree change rate) with a second decarburization determination model (a method for predicting carbon content by regression of characteristic values ​​of the RH decarburization process). The two models work together to achieve real-time online prediction of the decarburization endpoint of the automobile plate.

[0018] 1. The rate of change of vacuum degree predicts the carbon content.

[0019] When the carbon content of molten steel is high, a large amount of CO gas can be generated instantly, and the vacuum changes quickly; when the carbon content of molten steel is low, the reaction between carbon and oxygen in the molten steel weakens, the CO generation rate decreases, and the vacuum changes slowly. The vacuum change rate is strongly related to the amount of CO gas in the vacuum tank. The decarburization of molten steel can be predicted by the change in vacuum, as follows:

[0020] In the middle and late stages of RH decarburization, the change in vacuum degree in the vacuum tank is determined by the amount of waste gas, the amount of circulation, and the amount of gas leakage in the vacuum tank, namely:

[0021]

[0022] The annular flow and vacuum tank leakage can be regarded as constants. The main factor affecting the rate of change of vacuum degree is the exhaust gas volume, that is:

[0023]

[0024] The amount of waste gas is the amount of CO generated in the vacuum tank. The amount of CO generated is related to the carbon and oxygen in the molten steel. Formula (2) can be expressed as:

[0025]

[0026] In the middle and late stages of RH decarburization, the carbon content of molten steel is much lower than the oxygen content, that is, the carbon content is the limiting factor that determines the carbon-oxygen reaction rate. Therefore, the carbon content is the main factor that determines the amount of waste gas generated, and formula (3) can be expressed as follows:

[0027]

[0028] The carbon content of molten steel can be predicted by the vacuum degree change rate.

[0029] According to the above conclusions, combined with the actual production situation of Zhanjiang Iron and Steel, a method for determining the decarburization endpoint based on vacuum degree was developed. Specifically, the first decarburization determination model for predicting the decarburization endpoint based on vacuum degree change was constructed. According to the range of the carbon upper limit of the steel grade, the critical vacuum degree, the critical value of the vacuum degree change rate and the cumulative points of the change rate were set for the model to intervene in the determination. Among them, the cumulative points of the change rate refer to the occurrence of a calculated vacuum degree change rate ≤ the critical value of the vacuum degree change rate during the decarburization process, which is counted as one point. The specific setting logic is shown in Table 1.

[0030] Table 1 Logic of vacuum degree in determining decarburization endpoint

[0031]

[0032] Model specific determination process:

[0033] ① According to the range of the carbon upper limit of the steel grade, determine the critical vacuum degree, vacuum degree change rate critical value and change rate cumulative points for the model to intervene. The cumulative change rate points refer to the occurrence of a calculated vacuum degree change rate ≤ vacuum degree change rate critical value during the decarburization process, which is counted as one point.

[0034] ②The model calculates the vacuum degree change rate every 0.2 minutes.

[0035] ③ When the actual vacuum degree is less than or equal to the critical value of vacuum degree, the decarburization model starts to intervene in the judgment. When the calculated vacuum degree change rate is less than or equal to the critical value of vacuum degree change rate and the accumulated points meet the set requirements, the first condition for the end of decarburization is determined to be met.

[0036] 2. Predict carbon content by regression of process characteristic values.

[0037] During RH decarburization, the oxygen blowing amount V 1 , Decarburization time T 1 、The time T when the vacuum degree is ≤266pa 2 , scrap steel quantity M 1 、Aluminum addition amount M 2 、Toner quantity M 3 and decarbonization final oxygen C 1 It is the key characteristic value that affects decarburization. Based on historical data, the relationship between the carbon content of molten steel and the decarburization characteristic value is obtained through big data regression as follows:

[0038] W C =27.6+0.0111V 1 -0.0742T 1 +0.0454T 2 +0.00271M 1 +0.0349M 2 +0.0188M 3 -0.0228C 1 ;

[0039] The units of the characteristic values ​​in the above formula are: Oxygen blowing amount - Nm 3 ; Decarburization time - min; Time for maintaining vacuum degree ≤ 266 Pa - min; Scrap steel amount - kg; Amount of aluminum added - kg; Amount of carbon powder - kg; Final oxygen for decarburization - ppm.

[0040] During the RH decarburization process, the current characteristic value is read every 0.2 minutes to perform regression prediction on the carbon content. When the carbon content of the molten steel predicted by the second decarburization judgment model is ≤ the target carbon content, it is determined that the second condition for the end of decarburization is met.

[0041] In the RH decarburization process, when the first decarburization end condition and the second decarburization end condition are simultaneously met, it is determined that the automobile plate has reached the decarburization end point and the decarburization is ended.

[0042] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for determining the decarburization endpoint of RH automobile sheet, characterized in that: include: Construct the first decarburization judgment model for predicting the decarburization endpoint by vacuum degree change. According to the range of the carbon upper limit of the steel grade, set the critical vacuum degree, vacuum degree change rate critical value and change rate cumulative points for the model to start intervention judgment. During the RH decarburization process, the first decarburization judgment model calculates the vacuum degree change rate every 0.1-0.5min. When the actual vacuum degree is ≤ the vacuum degree critical value, the first decarburization model starts to intervene in the judgment. When the calculated vacuum degree change rate is ≤ the vacuum degree change rate critical value and the change rate cumulative points meet the set requirements, it is determined that the first condition for the end of decarburization is met. The second decarburization judgment model was constructed to predict the carbon content by regression of process characteristic values. During the decarburization process, the characteristic values ​​affecting decarburization include oxygen blowing volume V1, decarburization time T1, vacuum degree ≤ 266pa maintenance time T2, scrap steel volume M1, aluminum addition volume M2, carbon powder volume M3 and decarburization final oxygen C1. Based on historical data, the relationship between the carbon content y of molten steel and the characteristic values ​​affecting decarburization was obtained through big data regression as follows: y=27.6+0.0111V1-0.0742T1+0.0454T2+0.00271M1+0.0349M2+0.0188M3-0.0228C1; RH During the carbon process, the current characteristic value is read every 0.1-0.5min to perform regression prediction on the carbon content; When the carbon content of molten steel predicted by the second decarburization judgment model is less than or equal to the target carbon content, it is determined that the second condition for the end of decarburization is met; In the RH decarburization process, when the first decarburization end condition and the second decarburization end condition are simultaneously met, it is determined that the automobile plate has reached the decarburization end point and the decarburization is ended.

2. The method for determining the decarburization endpoint of RH automobile sheet according to claim 1, characterized in that: The first decarburization determination model calculates the vacuum degree change rate every 0.2 minutes.

3. The method for determining the decarburization endpoint of RH automobile sheet according to claim 1, characterized in that: The second decarbonization determination model reads the current characteristic value every 0.2 minutes and performs regression prediction on the carbon content.

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