Method of producing surface-treated steel sheet

Abstract

A method of producing a surface-treated steel sheet is provided. The method has a step of performing electrolytic treatment thereby to form a layer including a metal-oxygen compound on a surface of a steel sheet. The electrolytic treatment is performed so that the steel sheet is continuously fed into electrolytic treatment baths each including a treatment liquid and an electrode. The treatment liquid contains metal ions. The method is characterized in that: rolls provided for each of the electrolytic treatment baths (a roll for feeding the steel sheet into the electrolytic treatment bath and a roll for feeding the steel sheet out of the electrolytic treatment bath) comprise an energized roll that is electrically connected to a power source for flowing a direct current through the steel sheet and a non-energized roll that is not connected to a power source; and the energized roll is arranged such that, once the metal-oxygen compound has been formed by electrolytic treatment on a surface of the steel sheet to be in contact with the rolls, the metal-oxygen compound and the energized roll are not in contact with each other so as not to generate an arc spot.

1 . A method of producing a surface-treated steel sheet, the method comprising performing electrolytic treatment using an electrolytic treatment apparatus thereby to form a layer including a metal-oxygen compound on a surface of a steel sheet,
 the electrolytic treatment apparatus having electrolytic treatment baths each comprising a treatment liquid and at least one electrode,   the treatment liquid containing metal ions,   the electrolytic treatment being performed in each of the electrolytic treatment baths by continuously feeding the steel sheet into each of the electrolytic treatment baths and flowing a direct current between the steel sheet and the electrode, wherein:   the steel sheet is continuously fed by rolls into each of the electrolytic treatment baths, the rolls comprising a roll for feeding the steel sheet into the electrolytic treatment bath and a roll for feeding the steel sheet out of the electrolytic treatment bath, both of the rolls being provided for each of the electrolytic treatment baths;   the rolls provided in the electrolytic treatment apparatus comprise an energized roll that is electrically connected to a power source for flowing a direct current through the steel sheet and a non-energized roll that is not connected to a power source; and   the energized roll is arranged such that, once the layer has been formed by electrolytic treatment on a surface of the steel sheet to be in contact with the rolls, the layer and the energized roll are not in contact with each other so that an arc spot is prevented from occurring.   
     
     
         2 . The method of producing a surface-treated steel sheet according to  claim 1 , wherein, among the rolls provided in the electrolytic treatment apparatus, a roll for feeding the steel sheet into an electrolytic treatment bath that performs electrolytic treatment first for the surface of the steel sheet to be in contact with the rolls is the energized roll that is electrically connected to the power source for flowing the direct current through the steel sheet. 
     
     
         3 . A method of producing a surface-treated steel sheet, the method comprising performing electrolytic treatment using an electrolytic treatment apparatus thereby to form a layer including a metal-oxygen compound on a surface of a steel sheet,
 the electrolytic treatment apparatus having electrolytic treatment baths each comprising a treatment liquid and at least one electrode,   the treatment liquid containing metal ions,   the electrolytic treatment being performed in each of the electrolytic treatment baths by continuously feeding the steel sheet into each of the electrolytic treatment baths and flowing a direct current between the steel sheet and the electrode, wherein:   the steel sheet is continuously fed by rolls into each of the electrolytic treatment baths, the rolls comprising a roll for feeding the steel sheet into the electrolytic treatment bath and a roll for feeding the steel sheet out of the electrolytic treatment bath, both of the rolls being provided for each of the electrolytic treatment baths;   the rolls provided in the electrolytic treatment apparatus comprise at least one energized roll that is electrically connected to a power source for flowing a direct current through the steel sheet and a non-energized roll that is not connected to a power source; and   by adjusting combination of a resistance value of the layer on a surface of the steel sheet to be in contact with the at least one energized roll, a voltage applied to the at least one energized roll, and the number of the at least one energized roll to be provided, an arc spot is prevented from occurring when the steel sheet and the at least one energized roll are in contact with each other.   
     
     
         4 . A method of producing a surface-treated steel sheet, the method comprising performing electrolytic treatment in an electrolytic treatment bath thereby to form a layer including a metal-oxygen compound on a surface of a steel sheet,
 the electrolytic treatment bath comprising a treatment liquid and at least one electrode,   the treatment liquid containing metal ions,   the electrolytic treatment being performed in the electrolytic treatment bath by continuously feeding the steel sheet into the electrolytic treatment bath and flowing a direct current between the steel sheet and the electrode, wherein:   the steel sheet is continuously fed into the electrolytic treatment bath by a first roll for feeding the steel sheet into the electrolytic treatment bath and a second roll for feeding the steel sheet out of the electrolytic treatment bath;   the first roll is an energized roll that is electrically connected to a power source for flowing a direct current through the steel sheet; and   the second roll is a non-energized roll that is not connected to a power source.   
     
     
         5 . The method of producing a surface-treated steel sheet according to  claim 1  wherein the treatment liquid contains ions of at least one kind of metal selected from Zr, Al and Ti. 
     
     
         6 . The method of producing a surface-treated steel sheet according to  claim 1 , wherein pH of the treatment liquid is 2 to 5. 
     
     
         7 . The method of producing a surface-treated steel sheet according to  claim 1 , wherein a surface of the layer formed on the surface of the steel sheet has an electrical resistance value of 0.1 Ω or more. 
     
     
         8 . The method of producing a surface-treated steel sheet according to  claim 1 , wherein a molar amount of metal m the layer formed on the surface of the steel sheet is 0.5 mmol/m 2  or more. 
     
     
         9 . The method of producing a surface-treated steel sheet according to  claim 1 , wherein the layer formed on the surface of the steel sheet has a thickness of 15 nm or more. 
     
     
         10 . A surface-treated steel sheet for metal cans produced using the method of producing a surface-treated steel sheet according to  claim 1 .