Method of production of high flux density grain-oriented silicon steel sheet

Abstract

The present invention is a method of using a continuous casting-continuous hot rolling facility to cast a medium thickness bar, making the bar reach a final hot rolling inlet while a temperature over 1200° C. for holding the solid-solute state of AlN is maintained, hot rolling the bar, and rapidly cooling it to make fine AlN precipitate and thereby efficiently an inexpensively produce high flux density grain-oriented silicon steel sheet without any high temperature heating of the bar.

1 . A method of production of high flux density grain-oriented silicon steel sheet characterized by continuously casting a melt containing, by mass,
 C: 0.010 to 0.075%,   Si: 2.95 to 4.0%,   acid soluble Al: 0.010 to 0.040%,   N: 0.0010 to 0.0150%, and   one or both of S and Se in 0.005 to 0.1%   
     and
 having a balance of Fe and unavoidable impurities to produce a medium thickness bar of a thickness of 20 to 70 mm, holding said medium thickness bar at a temperature of over 1200° C. after casting, making it reach an inlet of a final hot rolling mill within 500 seconds from the completion of casting to starting continuous hot rolling, hot rolling to obtain a 1.5 mm to 5 mm thick hot rolled sheet, cooling with a cooling time from the end of hot rolling to reaching 600° C. in 150 seconds or less, then performing ordinary cold rolling, process annealing, decarburization annealing, final annealing, etc. 
 
   
   
       2 . A method of production of high flux density grain-oriented silicon steel sheet as set forth in  claim 1 , characterized by further including in said melt at least one element selected from the group of Sb: 0.005 to 0.2%, Nb: 0.005 to 0.2%, Mo: 0.003 to 0.1, Cu: 0.02 to 0.2%, and Sn: 0.02 to 0.3% precipitating at grain boundaries to inhibit crystal growth. 
   
   
       3 . A method of production of high flux density grain-oriented silicon steel sheet as set forth in  claim 1 , characterized by making said medium thickness bar reach the inlet of the final hot rolling mill within 500 seconds at the longest when holding it at a temperature of 1250° C. or more and within 150 seconds when holding it at a temperature of 1200° C. or more. 
   
   
       4 . A method of production of high flux density grain-oriented silicon steel sheet as set forth in  claim 1 , characterized by heating the medium thickness bar by a heating furnace to hold it at a temperature of 1300 to 1350° C. when the time required for making the medium thickness bar produced by continuous casting reach the inlet of the final hot rolling mill and starting the continuous hot rolling is over 200 seconds or when the temperature of said medium thickness bar is a low temperature such as 1000° C.