| abstract |
The hot rolled steel sheet for processing is, in mass%, C = 0.01 to 0.2%, Si = 0.01 to 0.3%, Mn = 0.1 to 1.5%, P ≤ 0.1%, S ≤ 0.03%, Al = 0.001 to 0.1%, N ≤ 0.006%, the remainder is Fe and an unavoidable impurity, the microstructure of which has a polygonal ferrite and a hard second phase having a main phase, the volume fraction of the hard second phase is 3 to 20%, and the hardness ratio (hard The second phase hardness / polygonal ferrite hardness) is 1.5 to 6, and the particle size ratio (polygonal ferrite particle size / hard second phase particle size) is 1.5 or more.n n n n Hot rolled steel, polygonal ferrite, volume fraction, hardness ratio, particle diameter ratio |