Continuous annealing line, continuous annealing method, method of producing cold-rolled steel sheet, and method of producing coated or plated steel sheet

Abstract

Provided are a continuous annealing line, a continuous annealing method, a method of producing a cold-rolled steel sheet, and a method of producing a coated or plated steel sheet that precisely predict a phase fraction of a steel sheet under a high temperature condition and rapidly adjust an annealing condition to reflect a predicted phase fraction variation. The continuous annealing line is for a steel sheet and includes a heating zone ( 6 ), a soaking zone ( 7 ), and a cooling zone ( 8 ), in this order, at least one induction heating device ( 9 ) disposed between the soaking zone ( 7 ) and the cooling zone ( 8 ), and a control device that sets operating conditions of the induction heating device based on a phase fraction during annealing obtained by a phase fraction prediction model.

1 . A continuous annealing line for a steel sheet, comprising a heating zone, a soaking zone, and a cooling zone, in this order, and further comprising:
 at least one induction heating device disposed between the soaking zone and the cooling zone; and   a control device configured to set an operating condition of the induction heating device based on a phase fraction during annealing obtained by a phase fraction prediction model.   
     
     
         2 . The continuous annealing line according to  claim 1 , wherein the phase fraction prediction model is a machine learning model generated using labeled data in which composition, a dimension, and a temperature of the steel sheet and an operating condition of a continuous annealing furnace are input variables and the phase fraction of the steel sheet during annealing is an output variable. 
     
     
         3 . The continuous annealing line according to  claim 2 , wherein the dimension of the steel sheet includes the thickness of the steel sheet,
 the temperature of the steel sheet includes steel sheet temperature immediately before the start of heating and the maximum arrival temperature of the induction heating device, and   the operating condition of the continuous annealing furnace includes the line speed of the steel sheet.   
     
     
         4 . A continuous annealing method for a steel sheet that is passed through a heating zone, a soaking zone, and a cooling zone, in this order, wherein
 at least one induction heating device is disposed between the soaking zone and the cooling zone, the method comprising:   a step of setting an operating condition of the induction heating device based on a phase fraction during annealing obtained by a phase fraction prediction model.   
     
     
         5 . The continuous annealing method according to  claim 4 , wherein the phase fraction prediction model is a machine learning model generated using labeled data in which composition, a dimension, and a temperature of the steel sheet and an operating condition of a continuous annealing furnace are input variables and the phase fraction of the steel sheet during annealing is an output variable. 
     
     
         6 . The continuous annealing method according to  claim 5 , wherein
 the dimension of the steel sheet includes the thickness of the steel sheet,   the temperature of the steel sheet includes steel sheet temperature immediately before the start of heating and the maximum arrival temperature of the induction heating device, and   the operating condition of the continuous annealing furnace includes the line speed of the steel sheet.   
     
     
         7 . The continuous annealing method according to  claim 4 , wherein
 the induction heating device heats the steel sheet at a rate of 10° C./s or more and 200° C./s or less, and   cooling of the steel sheet in the cooling zone is started in 10 s or less after the end of heating by the induction heating device.   
     
     
         8 . A method of producing a cold-rolled steel sheet, the method comprising annealing of the steel sheet, which is a cold-rolled steel sheet, by an annealing method adjusted by the continuous annealing method according to  claim 7 . 
     
     
         9 . A method of producing a coated or plated steel sheet, the method comprising applying a coating or plating treatment to a surface of the steel sheet annealed by the method of producing a cold-rolled steel sheet according to  claim 8 . 
     
     
         10 . The method of producing a coated or plated steel sheet according to  claim 9 , wherein the coating or plating treatment is electrogalvanization treatment, hot-dip galvanizing treatment, or galvannealing treatment.