Patent ID: 6364963
Filing Date: 2002-04-02
Classification: C21D

Abstract:
A process for making a grain oriented electrical steel sheet having a very low iron loss, comprising the steps of:heating to about 1300Â° C. or higher a steel slab containing about 1.5 to 7.0 wt % of Si, about 0.010 to 0.040 wt % of Al and/or about 0.0003 to 0.040 wt % of B as inhibitor elements, about 0.005 to 2.5 wt % of S and Se alone or in combination and about 0.0010 to 0.0100 wt % of N, about 0.005 to 2.5 wt % of at least one element selected from the group consisting of Mn, Cu, Sn, Ge, Bi, V, Nb, Cr, Te, Mo, and P, wherein P is in an amount 0.30 wt % or less when present expressed as a single species or a total of two or more species thereof, as inhibitor auxiliary elements, about 0.02 to 1.0 wt % of Ni, about 0.02 to 0.10 wt % of C, and about 0.005 to 0.15 wt % of Sb, wherein the respective relationships among the components of said slab are as follows: 5(xâˆ’0.05)&lE;y&lE;10x andâˆ’0.6x+0.06&lE;z&lE;âˆ’0.6x+0.11; wherein x represents the Sb content (wt %); y represents the Ni content (wt %); and z represents the C content (wt %); andcomprising as the remainder incidental impurities and Fe, hot rolling, cold-rolling once or several times to obtain a final thickness, and final annealing after decarburization annealing, and a hot roll sheet annealing conducted at a temperature over 900Â° C. or an intermediate annealing conducted at a temperature of over 900Â° C. after the hot rolling and prior to the final annealing, wherein the outlet temperature of hot rolling is controlled to between about 900Â° C. and about 1150Â° C.; wherein a first annealing of the annealing conducted at a temperature over 900Â° C. is conducted at heating rate of about 2 to 30Â° C./second between about 700 to 900Â° C.; and wherein H2 is present in the atmosphere at least from about 900Â° C. in a heating step in said final annealing step, and wherein N2 is present in said atmosphere at least up to about 1000Â° C.