Hot-rolled steel sheet for nitride having excellent fatigue strength, cold-rolled steel sheet and a method of manufacturing nitride, as well as automobile parts having excellent fatigue strength with them

Particularly suitable amount of Cr, a steel containing V, and B, the dislocation density within 50μm from the surface in the thickness direction, compared to the dislocation density of 1/4 position in the plate thickness direction, 2.0 times or more, in hot-rolled steel sheet or cold-rolled steel sheet nitriding nitriding excellent in fatigue strength is 10.0 times or less, the process after pickling the hot-rolled steel sheet or cold-rolled steel sheet having the ingredients, 0 in reduction ratio. is from 5 to 5.0 percent, the ratio of the mill load the steel plate line load F divided by the width (kg / mm) and per unit area is loaded in the longitudinal direction of the steel sheet load T (kg / mm