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Abstract

A method for the production of hot-rolled steel strip comprising the following steps: providing a steel slab comprising, in weight percentages: Si: 2.5 to 3.5%, C: 0.05 to 0.1%, Mn: 0:05 to 0.1%, Als: 0.015 to 0.026%, N: 0.0050 to 0.0100%, and further comprising S and/or Se so that S+ (32/79) Se is in an amount of 0.018 to 0.030%, and optionally comprising one or more elements chosen among Sb in an amount of 0.015 to 0.035%, Cu in an amount of 0.08% to 0.25%, Sn in an amount of 0.06% to 0.15%, P in an amount of 0.005% to 0.015%, the balance being iron and unavoidable impurities, reheating said slab to a temperature between 1300° C. and 1430° C., roughing hot-rolling said slab to produce a blank having a thickness below 50 mm, finishing hot-rolling of said blank to produce a hot rolled strip in three rolling passes or more, the temperature of said blank during the first pass being above 1150° C. and at least one rolling pass being performed with a reduction of 40% or more and being immediately followed by a holding of more than 20 sec, the average interpass holding temperature Tav being settled between 1000 and 1200° C., the total finishing hot rolling time t being controlled so that the value of Tav for any portion of said strip further respects the under mentioned equation: T_av>T₁+α₁(t−78) [eq. 1] with T₁=992.2+1493(Als) and α₁=1.204+24.9(Als), T_av and being expressed in ° C., t in seconds and Al_s in weight %, cooling of said hot-rolled strip from the finish rolling temperature to a temperature below 600° C. in less than 10 sec and coiling of said hot-rolled strip.

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First Claim