Hot-rolled steel sheet

Abstract

This hot-rolled steel sheet has a desired chemical composition and microstructure, an average sphere equivalent radius of alloy carbides in the ferrite is 0.5 nm or more and less than 10.0 nm, an average number density of the alloy carbides in the ferrite is 0.10×10 16 pieces/cm 3 or more and less than 1.45×10 16 pieces/cm 3 , an E value that indicates periodicity of the microstructure is 10.7 or more, and an I value that indicates uniformity of the microstructure is 1.020 or more, and a standard deviation of Mn concentration is 0.60 mass % or less.

1 . A hot-rolled steel sheet comprising, in terms of mass %, as a chemical composition:
 C: 0.050% to 0.250%;   Si: 0.05% to 3.00%;   Mn: 1.00% to 4.00%;   one or two er-more of Ti, Nb, and V: 0.060% to 0.500% in total;   sol. Al: 0.001% to 2.000%;   P: 0.100% or less;   S: 0.0300% or less;   N: 0.1000% or less;   O: 0.0100% or less;   Cu: 0% to 2.00%;   Cr: 0% to 2.00%;   Mo: 0% to 1.00%;   Ni: 0% to 2.00%;   B: 0% to 0.0100%;   Ca: 0% to 0.0200%;   Mg: 0% to 0.0200%;   REM: 0% to 0.1000%;   Bi: 0% to 0.0200%;   As: 0% to 0.100%;   one or more of Zr, Co, Zn, and W: 0% to 1.00% in total;   Sn: 0% to 0.05%; and   a remainder comprising Fe and impurities,   wherein, a microstructure has, in terms of area %,
 residual austenite at less than 3.0%, 
 ferrite at 15.0% or more and less than 60.0%, and 
 pearlite at less than 5.0%, 
   an average sphere equivalent radius of alloy carbides in the ferrite is 0.5 nm or more and less than 10.0 nm,   an average number density of the alloy carbides in the ferrite is 0.10×10 16  pieces/cm 3  or more and less than 1.45×10 16  pieces/cm 3 ,   an E value that indicates periodicity of the microstructure is 10.7 or more,   an I value that indicates uniformity of the microstructure is 1.020 or more, and   a standard deviation of Mn concentration is 0.60 mass % or less.   
     
     
         2 . The hot-rolled steel sheet according to  claim 1 , wherein the chemical composition comprises, in terms of mass %, one or more of:
 Cu: 0.01% to 2.00%;   Cr: 0.01% to 2.00%;   Mo: 0.01% to 1.00%;   Ni: 0.02% to 2.00%;   B: 0.0001% to 0.0100%;   Ca: 0.0005% to 0.0200%;   Mg: 0.0005% to 0.0200%;   REM: 0.0005% to 0.1000%;   Bi: 0.0005% to 0.0200%; and   As: 0.001% to 0.100%.