Hot-rolled steel sheet and method for manufacturing the same

Abstract

A hot-rolled steel sheet has a chemical composition containing, by mass %, C: 0.10% or less, Si: 2.0% or less, Mn: 2.0% or less, P: 0.100% or less, S: 0.02% or less, Al: 1.5% or less, and O: 0.0025% or less, the balance being Fe and incidental impurities, in which a main phase is ferrite, and a maximum orientation density of grains is 2.1 or less.

1 . A hot-rolled steel sheet, having a chemical composition comprising, by mass %:
 C: 0.10% or less,   Si: 2.0% or less,   Mn: 2.0% or less,   P: 0.100% or less,   S: 0.02% or less,   Al: 1.5% or less, and   O: 0.0025% or less, the balance being Fe and incidental impurities,   wherein a main phase is ferrite, and a maximum orientation density of grains is 2.1 or less.   
     
     
         2 . The hot-rolled steel sheet according to  claim 1 , wherein a maximum orientation density of grains is 1.5 or less in a plane inclined in a thickness direction at an angle of 45° with respect to a surface of the sheet from a direction perpendicular to a rolling direction. 
     
     
         3 . The hot-rolled steel sheet according to  claim 1 , wherein the chemical composition further contains one or two or more selected from, by mass %:
 Cr: 0.005% to 2.0%,   Ti: 0.005% to 0.20%,   Nb: 0.005% to 0.20%,   Mo: 0.01% to 2.0%,   V: 0.01% to 1.0%,   Cu: 0.01% to 4.0%,   Ni: 0.005% to 2.0%,   B: 0.0001% to 0.01%,   Ca: 0.0001% to 0.0050%,   REM: 0.0001% to 0.0050%,   Sb: 0.0010% to 0.10%, and   Sn: 0.0010% to 0.10%.   
     
     
         4 . The hot-rolled steel sheet according to  claim 2 , wherein the chemical composition further contains one or two or more selected from, by mass %:
 Cr: 0.005% to 2.0%,   Ti: 0.005% to 0.20%,   Nb: 0.005% to 0.20%,   Mo: 0.01% to 2.0%,   V: 0.01% to 1.0%,   Cu: 0.01% to 4.0%,   Ni: 0.005% to 2.0%,   B: 0.0001% to 0.01%,   Ca: 0.0001% to 0.0050%,   REM: 0.0001% to 0.0050%,   Sb: 0.0010% to 0.10%, and   Sn: 0.0010% to 0.10%.   
     
     
         5 . A method for manufacturing a hot-rolled steel sheet, comprising:
 heating a slab to 1,100° C. or higher, the slab having the chemical composition according to  claim 1 ;   performing rolling in 6 passes or more at a rolling reduction of 15% or more per pass in a temperature range of 1,000° C. or higher;   then performing rolling under conditions in which the rolling is performed in 3 passes or more in a temperature range of lower than 1,000° C. at a rolling reduction of 15% or more per pass, a rolling time is 2.0 seconds or less in a temperature range of lower than 1,000° C., and a final pass rolling temperature is 850° C. to 940° C.; and   subsequently performing cooling to 700° C. at an average cooling rate of 50° C./s or more, and performing coiling at 580° C. to 700° C.   
     
     
         6 . A method for manufacturing a hot-rolled steel sheet, comprising:
 heating a slab to 1,100° C. or higher, the slab having the chemical composition according to  claim 3 ;   performing rolling in 6 passes or more at a rolling reduction of 15% or more per pass in a temperature range of 1,000° C. or higher;   then performing rolling under conditions in which the rolling is performed in 3 passes or more in a temperature range of lower than 1,000° C. at a rolling reduction of 15% or more per pass, a rolling time is 2.0 seconds or less in a temperature range of lower than 1,000° C., and a final pass rolling temperature is 850° C. to 940° C.; and   subsequently performing cooling to 700° C. at an average cooling rate of 50° C./s or more, and performing coiling at 580° C. to 700° C.