Control device for vacuum degassing line, control method for vacuum degassing line, operation method, and method of producing molten steel

Abstract

A control device ( 10 ) for a vacuum degassing line includes an operation information input unit ( 11 ) configured to receive information regarding a weight and concentrations of components of the molten steel before the decarburization processing, track records of operation when the decarburization processing is being executed, and information regarding auxiliary raw materials; a component calculation unit ( 12 ) configured to estimate an in-molten-steel carbon concentration in the molten steel; a correction calculation unit ( 13 ) configured to calculate correction parameters to correct an estimated value of carbon content discharged from the vacuum degassing line and the estimated in-molten-steel carbon concentration in the molten steel; and a decarburization processing control unit ( 14 ) configured to end the decarburization processing when the in-molten-steel carbon concentration in the molten steel that has been corrected by the correction parameter reaches a target value.

1 . A control device for a vacuum degassing line that controls operations of the vacuum degassing line that performs decarburization processing by placing molten steel under a reduced pressure environment, the control device comprising:
 an operation information input unit configured to receive information regarding a weight and concentrations of components of the molten steel before the decarburization processing, track records of operation including measurement results of flow rate and concentrations of components of exhaust gas discharged from the vacuum degassing line when the decarburization processing is being executed, and information regarding auxiliary raw materials charged when the decarburization processing is being executed;   a component calculation unit configured to estimate an in-molten-steel carbon concentration in the molten steel, based on the information regarding the weight and the concentrations of components of the molten steel before the decarburization processing and the track records of operation;   a correction calculation unit configured to calculate correction parameters to correct an estimated value of carbon content discharged from the vacuum degassing line and the estimated in-molten-steel carbon concentration in the molten steel, based on the estimated in-molten-steel carbon concentration in the molten steel, the measurement results of flow rate and concentrations of components of exhaust gas, and a result of carbon balance calculation; and   a decarburization processing control unit configured to end the decarburization processing when the in-molten-steel carbon concentration in the molten steel that has been corrected by the correction parameter reaches a target value.   
     
     
         2 . The control device according to  claim 1 , wherein the correction calculation unit calculates the correction parameters in accordance with an evaluation function based on a difference between an amount of decrease in carbon content in the molten steel and a carbon content in exhaust gas. 
     
     
         3 . The control device according to  claim 2 , wherein the evaluation function includes a term based on a squared value calculated by subtracting the carbon content in the exhaust gas from a carbon content in the molten steel and a carbon content in the auxiliary raw materials, and a term based on a squared value of a difference between a carbon content in exhaust gas per unit time and a decarburization rate. 
     
     
         4 . The control device according to  claim 2 , wherein the evaluation function includes the correction parameter for a measured value of exhaust gas that is set as a correction coefficient to be multiplied by a value before correction. 
     
     
         5 . A control method for a vacuum degassing line configured to be executed by a control device for the vacuum degassing line that controls operations of the vacuum degassing line that performs decarburization processing by placing molten steel under a reduced pressure environment, the control method comprising:
 an input step of receiving information regarding a weight and concentrations of components of the molten steel before the decarburization processing, track records of operation including measurement results of flow rate and concentrations of components of exhaust gas discharged from the vacuum degassing line when the decarburization processing is being executed, and information regarding auxiliary raw materials charged when the decarburization processing is being executed;   a component calculation step of estimating an in-molten-steel carbon concentration in the molten steel, based on the information regarding the weight and the concentrations of components of the molten steel before the decarburization processing and the track records of operation;   a correction calculation step of calculating correction parameters to correct an estimated value of carbon content discharged from the vacuum degassing line and the estimated in-molten-steel carbon concentration in the molten steel, based on the estimated in-molten-steel carbon concentration in the molten steel, the measurement results of flow rate and concentrations of components of exhaust gas, and a result of carbon balance calculation; and   a decarburization processing end step of ending the decarburization processing when the in-molten-steel carbon concentration in the molten steel that has been corrected by the correction parameter reaches a target value.   
     
     
         6 . The control method according to  claim 5 , wherein the correction calculation step calculates the correction parameters in accordance with an evaluation function based on a difference between an amount of decrease in carbon content in the molten steel and a carbon content in exhaust gas. 
     
     
         7 . The control method according to  claim 6 , wherein the evaluation function includes a term based on a squared value calculated by subtracting the carbon content in the exhaust gas from a carbon content in the molten steel and a carbon content in the auxiliary raw materials, and a term based on a squared value of a difference between a carbon content in exhaust gas per unit time and a decarburization rate. 
     
     
         8 . The control method according to  claim 6 , wherein the evaluation function includes the correction parameter for a measured value of exhaust gas that is set as a correction coefficient to be multiplied by a value before correction. 
     
     
         9 . An operation method comprising operating a vacuum degassing line, by executing the control method according to  claim 5 . 
     
     
         10 . A method of producing molten steel comprising producing refined molten steel, by refining molten steel in a vacuum degassing line that is operated by the operation method according to  claim 9 .