Hot-rolled steel sheet for nitridation excellent in fatigue strength, cold-rolled steel sheet and a method of manufacturing nitride automotive parts and excellent in fatigue strength using them,

摘要

In particular, an appropriate amount of Cr, V, and a steel containing B, dislocation density of less than 50μm in the thickness direction from the surface, compared to the dislocation density of the position of the thickness direction of the quarter, 2.0 times or more, In hot-rolled steel sheet or cold-rolled steel sheet for nitride for nitride excellent in fatigue strength is 10.0 times or less, in their preparation after pickling the hot-rolled steel sheet or cold-rolled steel sheet having the components, reduction rate of 0. is a 5 to 5.0%, the ratio of the rolling mill load linear load was divided by the steel plate width F (kg / mm) and a load per unit area to be loaded in the longitudinal direction of the steel plate T (kg / mm ²⁾ , F / T is characterized in that applying a skin pass rolling at 8000 above conditions, and even a motor vehicle part which is nitrided by molding them hot-rolled steel sheet or cold rolled steel.